Lilies of Blood

The flora of southern Africa is renowned for being remarkably diverse and, in many cases, remarkably eye-catching. The region is home to more than its fair share of ornamental plants, many of which have become popular garden subjects. Among the remarkable members of the southern African flora are the blood lilies of the genus Haemanthus.

Haemanthus coccineus, copyright Peter Coxhead.

Haemanthus is a genus of 22 known species found in the very southern part of the continent, in the countries of South Africa and Namibia (species from further north that have historically been included in Haemanthus are now treated as a separate genus Scadoxus). It is a member of the belladonna family Amaryllidaceae and, like many other members of that family, grows as a herb from a fleshy bulb that is partially or entirely concealed underground. The plant above ground may be annual or persistent, depending on species. Each individual Haemanthus plant produces very few leaves at a time: two is the most common number (Van Jaarsveld 2020). The leaves are more or less fleshy, often hairy, and may be directed upwards or spread outwards.

In those species that shed their leaves, flower stalks are produced before the next season's leaves appear, in a similar matter to the related naked ladies Amaryllis belladonna. Flowers are produced in dense umbels, subtended by bracts that are often brightly coloured, so at a glance the inflorescence of some species might be taken for a single large flower up to ten centimetres in diameter. Depending on the species, the supporting stalk may vary from over a foot in height to only a few centimetres. The first species to be described bear flowers of a bright red colour, explaining both the genus and vernacular names, but flowers may also be pale pink or white. Species that lack the red colour may be referred to as 'paintbrush lilies' rather than 'blood lilies'. Fruits are soft fleshy berries.

Haemanthus albiflos, copyright Krzysztof Ziarnek, Kenraiz.

Phylogenetic analyses of the genus have identified two major clades, a mostly eastern clade found in regions with summer rainfall and a mostly western clade associated with winter rainfall. A notable outlier is the eastern summer-rainfall species H. montanus which is the sister taxon to the winter rainfall clade. Members of the summer-rainfall clade have white or pale pink flowers; members of the winter-rainfall clade have pale pink to dark red flowers. Members of both clades have been grown as pot plants for their unusual appearance though the scent of the flowers is not regarded as pleasant. Perhaps the most widely grown species is H. albiflos, a species native to both the western and eastern parts of South Africa that bears flowers in umbels up to seven centimetres wide. This species is evergreen, carrying its leaves year-round.

REFERENCE

Van Jaarsveld, E. 2020. Haemanthus. In: Eggli, U., & R. Nyffeler (eds) Illustrated Handbook of Succulent Plants: Monocotyledons 2^nd ed. pp. 441–443. Springer.

Woolly Orchids

The orchids of the Orchidaceae are widely recognised as one of the most diverse families of plants in the modern world, both in number of species and morphologically. They are readily distinguished from other flowering plants by a unique combination of features including the fusion of the male and female organs of the flower into a central column. Rather than being released as individual grains, pollen is aggregated into compact masses called pollinia that are attached to pollinators as whole units. Most orchid species also have the lower of the flower's three petals enlarged and differentiated into a distinctive lip that may present a bewildering array of shapes and colours. Because of their striking and colourful appearance, many orchids have long attracted attention from humans and many are popular ornamentals. But there are also some major groups of orchids that have been more neglected and one such group is members of the subtribe Eriinae.

Dendrolirium tomentosum, copyright Orchi.

The Eriinae comprise about a thousand known species of orchid found mostly in the tropics of Asia and the west Pacific, with a handful of species described from Africa. Most are epiphytes and lithophytes (growing on rocks); a smaller number are terrestrial. Because the flowers of eriines tend to be fairly small and simple, they have attracted less notice than other members of the family, but in some parts of their range they are among the most abundant epiphytic orchids (Ng et al. 2018). Within the Orchidaceae, eriines are a subgroup of the subfamily Epidendroideae, characterised by compact, laterally compressed pollinia, and the tribe Podochileae, with duplicate leaves, a short and massive column, and often spherical silica cells in the stems (Szlachetko 1995). The features distinguishing Eriinae from other subtribes of Podochileae are more vague and there are reasons to believe the Eriinae ultimately represent the paraphyletic residue of the tribe once the more specialised subgroups are removed (Ng et al. 2018). One recent classification of the orchids recommended abandoning subtribes within the Podochileae altogether (Chase et al. 2015). Nevertheless, features characteristic of most eriines include a terminal or upper lateral inflorescence, eight pollinia per flower, and sticky caudicles on the pollinia composed of apical pollen grains. The lip is commonly divided into three lobes. Another common feature of the group (and the inspiration for the name of the type genus Eria, meaning 'woolly') is a covering of hairs on the flower and sometimes the inflorescence. In one genus, Trichotosia, the leaves are also hairy.

Ascidieria grandis, copyright Dick Culbert.

Historically, the majority of eriines have been included in a broad genus Eria. However, as with the subtribe as a whole, recent studies have indicated that this sense of Eria is not monophyletic and hence its species should probably be divided between several genera. Ng et al. (2018) recognised 21 genera among the eriines. The African species, previously placed in their own genus Stolzia, were united with the closely related Asian genus Porpax.

The pollination biology of eriines is, for the most part, not well known. Some have speculated that they were pollinated by beetles; one website I found showed pollinia attached to a gnat. The two species of the genus Callostylis have flowers whose appearance suggests pollination by pseudocopulation (tricking male insects into attempting to mate with them by mimicking females) but such flowers are unique within the Podochileae (Ng et al. 2018). At least some eriines have flowers producing 'pseudopollen' from broken-off hairs (Pansarin & Maciel 2017). This pseudopollen is collected and eaten by pollinators. Thus, though the most common means of attracting pollinators among orchids is via deception, at least some eriines are willing to pay their way in life.

REFERENCES

Ng, Y. P., A. Schuiteman, H. A. Pedersen, G. Petersen, S. Watthana, O. Seberg, A. M. Pridgeon, P. J. Cribb & M. W. Chase. 2018. Phylogenetics and systematics of Eria and related genera (Orchidaceae: Podochileae). Botanical Journal of the Linnean Society 186: 179–201.

Pansarin, E. R., & A. A. Maciel. 2017. Evolution of pollination systems involving edible trichomes in orchids. AoB Plants 9: plx033.

Szlachetko, D. L. 1995. Systema Orchidalium. Fragmenta Floristica et Geobotanica Supplementum 3: 1–152.

A Slipper of the Lip

The world of flowering plants includes many unusual and eye-catching examples but even among all this variety the orchids often stand out. Their remarkable array of colours and forms have long fascinated people around the world. One of the more distinctive of orchid subgroups is the Cypripedioideae, commonly known as the slipper orchids.

Pink slipper orchids Cypripedium acaule, copyright Sasata.

Slipper orchids get their name from their most easily recognisable feature, a flower with a deeply saccate labellum or lip (the lower of the three petals) that is supposed to resemble a slipper (an analogy presumably settled on because the alternative of 'scrotum orchid' doesn't have the same ring to it). Like many other orchids, slipper orchids attract pollinators through deception rather than offering a genuine reward. Pollinators are enticed into entering the lip through its large central opening but find themselves unable to exit the same way (presumably because of the way that the rim of the opening curls inwards). Instead, they are forced to make their exit through one of two smaller openings at the base of the lip where it joins the flower's central column. As the pollinator exits this way, it must crawl past the stigma and stamens, removing any pollen it might already be carrying and depositing a new load.

Dwarf slipper orchid Cypripedium fargesii, copyright Steve Garvie.

The exact manner in which the pollinator is lured in varies by species and target (Pemberton 2013). Many produce odours that mimic legitimate nectar-producing flowers or potential food sources such as carrion. A group of species in the genus Cypripedium that are pollinated by bumble bees have low-growing flowers with a purple lip whose main opening appears black. They therefore resemble the opening of a mouse-hole of the type bumble bees use as nest sites. The North American Cypripedium fasciculatum produces a mushroom-like smell that attracts diapriid wasps that parasitise fungus gnats. Some species of the genus Paphiopedilum have light-coloured spots or warts on the flower that are mistaken for a colony of fat, healthy aphids by egg-laying hover flies seeking a food source for their larvae. Perhaps one of the oddest known set-ups is found in the species Cypripedium fargesii whose hover fly pollinator normally feeds on fungal spores. The orchid lures the fly in with patches of hairs on its leave that resemble a fungal infection. A few slipper orchid species are known to be habitually self-pollinating without the intervention of a pollinator; one such species, the South American Phragmipedium lindenii, has lost the slipper-shaped labellum and instead has a lip resembling the other petals.

Selenipedium dodsonii, a species only described as recently as 2015, copyright Andreas Kay.

Slipper orchids have been recognised as a distinct group from other orchids since at least 1840. A number of features isolate them from other orchids, such as their possession of two functional stamens (most other orchids have flowers with only a single stamen). More recent phylogenetic studies have corroborated their position as one of the earliest-diverging orchid lineages. Over 170 species of slipper orchid are currently known, divided by most authors between five genera; most of these genera have widely separated geographic ranges. The genera Selenipedium and Cypripedium have plicate leaves (that is, leaves that are folded within the bud several times longitudinally, in the manner of a fan) that are widely spaced along a well-developed stem, and a prominent rhizome (Rosso 1966). Selenipedium is a small genus found in northern South America that may reach heights of five metres. It differs from the more diverse Cypripedium in having trilocular ovaries and a commonly branching stem; Cypripedium, with over fifty species found across the Holarctic region, has unilocular ovaries and never branches. Cypripedium is the most widely distributed of the slipper orchid genera; the North American C. passerinum may even be found growing in tundra.

Paphiopedilum Leeanum, a cultivated hybrid originally developed in Britain in the 1880s, copyright David Eickhoff.

Phylogenetic analysis of the slipper orchids places Selenipedium as the sister group of the other genera with Cypripedium the next to diverge (Cox et al. 1997). The remaining three genera likely form a single clade united by the possession of a condensed rhizome and conduplicate leaves (folded once in the bud along the midline) arranged in a basal rosette. Paphiopedilum is the most speciose genus of slipper orchids with over ninety species found in India and southeastern Asia; it is also the genus most commonly found in cultivation. Phragmipedium includes over 25 species found in Central and South America; one of these, the Peruvian P. kovachii, has the largest known flowers of any slipper orchid, reaching twelve centimetres in diameter. The third genus Mexipedium, includes a single species M. xerophyticum found in Oaxaca state in Mexico. The three conduplicate-leaved genera are less distinct than the other two genera (one notable distinction is that Phragmipedium has trilocular ovaries whereas those of Paphiopedilum and Mexipedium are unilocular) and it has been suggested that they should be merged into a single genus. Nevertheless, not only are they all geographically distinct, they are supported as monophyletic by molecular analysis (Cox et al. 1997).

Phragmipedium caudatum, copyright Eric Hunt.

Their dramatic appearance has made slipper orchids highly prized in cultivation or by flower collectors. Unfortunately, many species have been subject to over-collection as a result. Many of the temperate Cypripedium species now require intensive conservation management, and populations of some Paphiopedilum species have been driven close to extinction. Once again, it would be a tragedy if such a fascinating group of plants was to vanish from the world.

REFERENCES

Cox, A. V., A. M. Pridgeon, V. A. Albert & M. W. Chase. 1997. Phylogenetics of the slipper orchids (Cypripedioideae, Orchidaceae): nuclear rDNA ITS sequences. Plant Systematics and Evolution 208: 197–223.

Pemberton, R. W. 2013. Pollination of slipper orchids (Cypripedioideae): a review. Lankesteriana 13 (1–2): 65–73.

Rosso, S. W. 1966. The vegetative anatomy of the Cypripedioideae (Orchidaceae). Journal of the Linnean Society, Botany 59: 309–341.

The Most Australian of Plants

Imagine yourself standing in a remote corner of northern Australia. Before you stretches an expanse of rolling hills, extending as far as the eye can see. The hills are covered with a carpet of green. You step forward, eager to explore these open fields. But as you approach them, everything changes. What appeared to be a uniform carpet is actually dense tussocks, each separated by an underlay of bare gravel. And instead of soft, yielding blades, the tussocks offer you nothing but resin and hate. Welcome to spinifex country.

Grassland dominated by Triodia pungens (bright green) and T. basedowii (grey-green), copyright Hesperian.

The spinifexes of the genus Triodia are a uniquely Australian group of plants. Some North American grasses have been assigned to this genus in the past but have since been moved elsewhere. There is also a widespread genus of coastal grasses that formally goes by the name of Spinifex but that is something different again. In many parts of arid Australia (and arid Australia equals most of Australia), spinifexes are the dominant form of plant life. As noted above, they grow in tight tussocks that may reach remarkable sizes and densities: clumps of the largest species may reach 2.5 metres in height and six metres in diameter (Lazarides 1997). Not uncommonly, these largest patches will be ring-shaped due to the centre dying off while growth continues around the edges. The leaf blades are long, needle-shaped, woody and rigid. Speaking from experience, the sharp tips of these blades will break off all too easily, embedding themselves in the flesh of any passers by. And some idea of their rigidity will also be conveyed by the fact that, in the growth season, it was not uncommon to discover macabre shish kebabs made from jumping grasshoppers that had had the misfortune to land on the end of one.

Mature stand of Triodia irritans, showing the tendency of hummocks to grow into circles as the centre dies off. Copyright ANBG photo M. Fagg.

Nearly 70 species are currently recognised within the genus, often differing in their preferred microhabitat. One of the most common species, Triodia basedowii, extends its range across almost the entirety of the continent between 18 and 30 degrees South and west of the Great Dividing Range. This species has a preference for sandplains and dunefields. Other species are far more localised. Barrett & Barrett (2011) described two new species found in association with sandstone cliff faces in the Ragged Range in Western Australia. Triodia barbata was found only in a thin band along the top of the cliff faces and may have had a population of only about 300 individuals. The more abundant (but still not widespread) T. cremnophila was found only on the vertical faces of the cliffs themselves. However, it must be noted that large gaps may exist in our knowledge of the ranges of Triodia species because of the remoteness and difficulty of getting to many of the regions in which they are found (seriously, if you've never been to central Australia yourself, it is difficult to appreciate just how much Absolutely Nothing there is there). Triodia mollis is known from two widely separated regions in northern Western Australia and Queensland with no confirmed records as yet from the entire expanse of the Northern Territory in between.

Preferred habitat of Triodia cremnophila, from Barrett & Barrett (2011). Yes, it only grows on the cliff face. Yes, someone presumably went down the cliff face to get specimens.

Being as woody and harsh as it is, it should come as no surprise that relatively few animals are capable of eating spinifex. Many Australian termites, such as the endemic genus Drepanotermes, are spinifex specialists; workers of Drepanotermes may be seen leaving their nest at night to collect pieces of spinifex blades and carry them back. Pastoralists may refer to 'hard' and 'soft' spinifex varieties but the difference is one of degree only; even the 'soft' spinifexes (usually the resin-producing species) are pretty damn hard by the standards of any other grass. Livestock are sometimes grazed on spinifex when bettter options are unavailable, in which case patches of spinifex may be burnt off to encourage the production of younger, more palatable growth (spinifex burns exceedingly well but also grows back readily from the remnant rootstock). The resin from spinifex also has a history of being used by indigenous Australians as an adhesive when making tools. For the most part, though, the main value of spinifex remains in its role as the dominant vegetation and habitat for the areas where it is found.

REFERENCES

Barrett, R. L., & M. D. Barrett. 2011. Two new species of Triodia (Poaceae: Triodieae) from the Kimberley region of Western Australia. Telopea 13 (1–2): 57–67.

Lazarides, M. 1997. A revision of Triodia including Plectrachne (Poaceae, Eragrostideae, Triodiinae). Australian Systematic Botany 10: 381–489.

A Spoonful of Lemba

Lemba or hill coconut Curculigo latifolia, from here.

The south-east Asian plant known as lemba has been referred to briefly on this site before, as a member of the family Hypoxidaceae. As noted in that post, it has been through a couple of names over the years: some sources will refer to it as Molineria latifolia, while others will call it Curculigo latifolia. The genera Molineria and Curculigo have been distinguished based on the presence of beaked (Curculigo) or unbeaked (Molineria) fruits and seeds, but the phylogenetic analysis of Hypoxidaceae by Kocyan et al. (2011) did not find this character to correlate with phylogeny. They therefore proposed to stop recognising the two genera as distinct, merging all species under Curculigo.

Curculigo latifolia is one of the largest species in the Hypoxidaceae. It is mostly found growing in damp, shaded locations, and the long-petioled leaves coming from an erect central rhizome can be a metre in length. Its small yellow flowers are placed at the base of the plant, at ground level; this distinguishes this species from various large orchid species found in the same region that may also be referred to as 'lemba' (or 'lumbah', or some other spelling/linguistic variant). The flowers give rise to small white berries, about an inch in size, with a distinct beak.

Fruit cluster of Curculigo latifolia, from DQ Farm.

Uses of this plant were recently reviewed by Lim (2012). The leaves provide a strong, lightweight fibre that is used to make nets, rope and cloth. The roots are brewed to treat various illnesses. However, the feature of this plant that has received the most attention in recent years is the fruit. These are edible, and are said to taste a bit like a sweet cucumber. The reason they have aroused interest, though, is that after eating one, anything else eaten within the next ten minutes or so will also taste sweet. This effect has been traced to a protein in the fruit, variously called neoculin or curculin, that has been reported to have several hundreds times the sweetness relative to weight of sucrose. Curculin has consequently been proposed as a potential low-calorie sweetener (to which I say, I'm sure it can't possibly taste worse than stevia), though one limitation is that the protein becomes denatured at temperatures above fifty degrees and loses its sweetening properties. As yet, though, it doesn't look like lemba sweetener has made it onto the commercial market.

REFERENCES

Kocyan, A., D. A. Snijman, F. Forest, D. S. Devey, J. V. Freudenstein, J. Wiland-Szymańska, M. W. Chase & P. J. Rudall. 2011. Molecular phylogenetics of Hypoxidaceae—evidence from plastid DNA data and inferences on morphology and biogeography. Molecular Phylogenetics and Evolution 60 (1): 122-136.

Lim, T. K. 2012. Edible Medicinal and Non-Medicinal Plants, vol. 4. Fruits. Springer.

Lachenalia

Back in 2011, I presented you with a post on the southern African flowering bulb genus Ledebouria. In that post, I mentioned that Ledebouria was just one of a wide diversity of ornamental plants found in that part of the world.

Lachenalia elegans var. flava, from the Pacific Bulb Society.

Lachenalia, sometimes known as Cape cowslips, is a genus of over 100 species found in Namibia and South Africa. Most Lachenalia species sprout and flower in the winter. Lachenalia is not too distant a relative of Ledebouria—both are classified in the squill tribe Massonieae—and bears a distinct resemblance to the latter with its fleshy leaves that are often blotched with purple. Some species of Lachenalia share the geophyllous habit I described in the earlier post for some Ledebouria, with the leaves growing pressed closely to the ground. However, Lachenalia differs from Ledebouria in having flowers with well-developed bracts, and anthers arranged in two series. Also, while the scales of Ledebouria bulbs are often loose, though of Lachenalia bulbs are always tightly packed (Manning et al. 2004).

Lachenalia zebrina f. zebrina, photographed by Alan Horstmann.

Lachenalia species include some popular garden plants, to the extent that some are known as invasive weeds here in the Perth region. Nevertheless, a simple image search immediately shows why they are so popular. Varieties of this genus are available in reds, pinks, yellows, purples... One species, L. viridiflora, has flowers of a quite remarkable turqouise colour. Though revered in cultivation, L. viridiflora is critically endangered in the wild, with a range of only 19 km² in which it is threatened by grazing, housing development and (almost ironically) the collection of specimens for horticulture.

Lachenalia viridiflora, photographed by A. Harrower.

REFERENCE

Manning, J. C., P. Goldblatt & M. F. Fay. 2004. A revised generic synopsis of Hyacinthaceae in sub-Saharan Africa, based on molecular evidence, including new combinations and the new tribe Pseudoprospereae. Edinburgh Journal of Botany 60 (3): 533-568.

Star-Grass

Common star-grass Hypoxis hirsuta, photographed by Merel R. Black.

It does not require a great deal of insight to understand why the plant pictured above has acquired the vernacular names of 'star-grass' or 'gold-star'. This small native of North America is one of the few representatives in that region of the family Hypoxidaceae, a group of about 150 species of thin-leaved monocots that is most diverse in the Southern Hemisphere, particularly in Africa. Most Hypoxidaceae are small like the North American gold-star, though the Asian hill coconut Curculigo latifolia may be over a metre in height. All grow from underground corms or rhizomes. Their flowers have the typical monocot arrangement of three sepals and three petals, and are most commonly yellow to pink in colouration. They mostly produce little scent (some have a faint sweet scent), and usually attract pollinators by offering pollen as a reward. Some species are grown as ornamentals, but for the most part the Hypoxidaceae are not that significant economically. The tubers of the African potato Hypoxis hemerocallidea (which, despite its vernacular name, does not seem to be eaten as a vegetable per se) have been used to make a medicinal tea; it has become particularly widely used in recent years to supposedly alleviate the symptoms of HIV, but tests of its actual efficacy remain in progress.

Lemba or hill coconut Curculigo latifolia (previously Molineria latifola), photographed by Ahmad Fuad Morad.

Recent authors have recognised up to ten genera within the Hypoxidaceae, but a phylogenetic analysis of the family by Kocyan et al. (2011) lead them to suggest the reduction of that number to four or six, depending on how one might chose to deal with the position of Hypoxidia. This is a distinctive genus of two species found on the Seychelles. Flowers of Hypoxidia are a dark red-brown colour, and in contrast to the weak scent of other Hypoxidaceae they have a strong foetid odour that attracts flies as pollinators. Kocyan et al.'s phylogenetic analysis placed Hypoxidia as sister to the other species of Hypoxidaceae found on the Seychelles, Curculigo seychellensis, and the two together were placed as sister to a clade containing the remaining species of Curculigo (as well as species of Molineria, which Kocyan et al. suggested be synonymised with Curculigo). Curculigo species bear their flowers at the base of the plant; the ovary is actually found beneath the ground, with the corolla borne above the ground on an elongate tubular rostrum. This rostrum is particularly long in C. seychellensis, up to 12 cm. Curculigo seychellensis also has bifurcated leaves that make it look superficially like a palm seedling. It remains to be settled whether future authors will prefer to place C. seychellensis in its own new genus, or to sink Hypoxidia into Curculigo.

Pauridia capensis (previously Spiloxene capensis), photographed by Bob Rutemoeller.

The remaining Hypoxidaceae can be divided between the genera Hypoxis (containing Rhodohypoxis as a junior synonym), Empodium and Pauridia (containing Spiloxene and Saniella as synonyms, as well as some Australian species previously placed in Hypoxis). Members of the genera Empodium and Pauridia produce annual corms, while Hypoxis species have tuberous rhizomes. Empodium and Pauridia differ in features of the flowers and seeds (Kocyan et al. 2011). The two African Pauridia species previously classified as Saniella resemble Curculigo in having subterranean ovaries. It is perhaps unfortunate that the name Pauridia, previously restricted to two particularly small African species only a couple of centimetres in height, takes priority over Spiloxene, previously used for a larger group of about thirty species. But such are the vagaries of nomenclature, and that which we now call Pauridia capensis (Snijman & Kocyan 2013) will smell as... generally indifferent, actually, but it at least looks pretty specky.

REFERENCES

Kocyan, A., D. A. Snijman, F. Forest, D. S. Devey, J. V. Freudenstein, J. Wiland-Szymańska, M. W. Chase & P. J. Rudall. 2011. Molecular phylogenetics of Hypoxidaceae—evidence from plastid DNA data and inferences on morphology and biogeography. Molecular Phylogenetics and Evolution 60 (1): 122-136.

Snijman, D. A., & A. Kocyan. 2013. The genus Pauridia (Hypoxidaceae) amplified to include Hypoxis sect. Ianthe, Saniella and Spiloxene, with revised nomenclature and typification. Phytotaxa 116 (1): 19-33.

The Resurrection of Grass

The resurrection grass Oropetium thomaeum, photographed by Diana Margaret Napper.
Even for a grass, the annual Oropetium thomaeum is not a very prepossessing plant. Only a couple of inches in height, it can be found as small tufts in arid or saline habitats in tropical Africa and Asia. In some parts of India, it has been recorded as a dominant grass species, probably because its small size makes it resistant to grazing while, for instance, its somewhat taller perennial relative O. roxburghianum is restricted to growing under shrubs that protect it from hungry ruminants (Gaff & Bole 1986).

Despite its modesty, O. thomaeum is not devoid of interest. It is an example of what is known as a 'resurrection plant', able to survive severe desiccation in a dormant state only to apparently come back to life after rain. Because O. thomaeum is a diploid species with a relatively small genome (one of the smallest of all grasses), it has been touted as potential useful in studying the genetic factors controlling drought tolerance (Bartels & Mattar 2002). According to this article, it has seen some use in attempts to rehabilitate degraded environments. Oropetium thomaeum has also been shown to differ from most plant species in that it is the shoot that emerges first from the germinating seed rather than the root (Dakshini & Tandon 1970).

Oropetium is a small genus of seven species of grasses in the subfamily Chloridoideae, with three species found in India and five in Africa (Phillips 1975). Despite the small number of species, members of Oropetium have been divided between no less than five genera in the past, reflecting a fair degree of disparity in their reproductive morphology. All, however, are relatively small narrow-leaved grasses forming dense tufts. Whether the African species possess the resurrective abilities of the Asian species remains, so far, unknown.

REFERENCES

Bartels, D., & M. Z. M. Mattar. 2002. Oropetium thomaeum: a resurrection grass with a diploid genome. Maydica 47 (3-4): 185-192.

Dakshini, K. M. M., & R. K. Tandon. 1970. An unusual type of germination of graminaceous seed. Annals of Botany 34 (2): 423-425.

Gaff, D. F., & P. V. Bole. 1986. Resurrection grasses in India. Oecologia 71: 159-160.

Phillips, S. M. 1975. A review of the genus Oropetium (Gramineae). Kew Bulletin 30 (3): 467-470.

From Giant Reeds to Tiny Leaves

Giant reed Arundo donax, photographed by Russ Kleinman & Richard Felger.

The grasses are without a doubt one of the most successful groups of plants in the modern environment. So it is only fitting that for today's post I'm going to be looking at one of the subgroups of the grasses, the Arundinoideae.

The Arundinoideae, including the reeds and related species, has been long recognised as a subfamily of grasses, but rather vaguely so. Most of the characters of leaf anatomy previously used to define the group are either plesiomorphies or absences. Arundinoids use the plesiomorphic C₃ photosynthetic pathway rather than the derived C₄ pathway and lack the radiate leaf anatomy associated with C₄ photosynthesis. They also lack the fusoid leaf cells with accessory arm cells that are characteristic of the bamboos. In other features, 'arundinoids' were quite variable, and it therefore came as no surprise to anyone when phylogenetic analyses indicated that the group was polyphyletic. As a result, the Grass Phylogeny Working Group (2001) divided the arundinoids between a number of subfamilies, separating the wiregrasses as the Aristidoideae and the oatgrasses and pampas grasses as the Danthonioideae. This reduced the Arundinoideae proper, previously including well over 600 species, to less than 40.

Common reed Phragmites australis, from here.

Even so, the arundinoids remain a disparate group, and morphological synapomorphies of the group remain elusive. The taxonomic core of the group, the reeds of the genera Arundo, Phragmites and Molinia, are connected by the possession of hollow culm internodes, a punctiform hilum (the detachment scar on the 'seed') and convex adaxial rib sides in the leaf blade (Grass Phylogeny Working Group 2001), but these features are not shared by all other arundinoids. The reeds are found in damp habitats, and the common reed Phragmites australis can grow in standing water. The largest species, the giant reed Arundo donax, can reach a height of ten metres under ideal growth conditions. In contrast, the Tom Thumb grass Dregeochloa pumila is found in the Namib Desert of South Africa and Namibia, and doesn't reach any higher than 25 mm (excluding the flower stalk, which may give it another inch or so). Dregechloa pumila is also remarkable as the only succulent species of grass. Also included in the Arundinoideae are the crinipoid grasses, a somewhat poorly known assemblage of species found in highlands of Africa, Madagascar and southern India (Linder et al. 1997).

Tom Thumb grass Dregechloa pumila, from Ernst van Jaarsveld.

Arundo donax has become known in some areas as an agressive weed, particularly in the US. It has one of the fastest growth rates of any plant, potentially up to ten centimetres in a single day (remember, that's four Dregeochloas!) Despite its invasive potential, some have been promoting it as a potential crop species, particularly for the biofuel market (presenting its fast growth rate as an outright advantage). Arundo donax is also the preferred material for woodwind reeds. Phragmites australis (also a problematic weed in the wrong circumstances) has been used in wastewater purification, and Wikipedia also notes that it is edible, quoting that the young stems "while still green and fleshy, can be dried and pounded into a fine powder, which when moistened is roasted like marshmallows". 'Like' marshmallows, perhaps, but I don't think that I'll be rushing to make the substitution.

REFERENCES

Grass Phylogeny Working Group. 2001. Phylogeny and subfamilial classification of the grasses (Poaceae). Annals of the Missouri Botanical Garden 88 (3): 373-457.

Linder, H. P., G. A. Verboom & N. P. Barker. 1997. Phylogeny and evolution in the Crinipes group of grasses (Arundinoideae: Poaceae). Kew Bulletin 52 (1): 91-110.

Patterns on a Squill

Violet squill Ledebouria socialis, photographed by Stan Shebs.

The south of Africa is one of the world's centres for botanical diversity. Home to an abundance of the floristically wierd and wonderful, you might be surprised to know just how many of your favourite garden plants (assuming that you have favourite garden plants) originate from that part of the world: proteas, leucadendrons, red-hot pokers (Kniphofia), freesias, agapanthus*... to name a few. The subject of today's post, the genus Ledebouria, is perhaps not one of the best known of the southern African contributions to horticulture, but it's none the less noteworthy.

*Well, personally, I'm not that fussed on agapanthus ('orrible weedy things), but a not insignificant number of people would disagree with me on that point.

Ledebouria revoluta, from here.

Ledebouria is a genus of the plant family Hyacinthaceae that also includes such familiar plants as hyacinths and bluebells, and within that family to a group known as squills. Like other members of the family, Ledebouria species are bulbiferous with developed leaves only present for part of the year. There are about forty or more species of Ledebouria in southern Africa, with outliers in Madagascar and India (Manning et al. 2004), though the number of species varies according to whether or not the genera Drimiopsis and Resnova are treated separately. Molecular analyses have tended to fail to distinguish the three genera, but morphological and combined analyses support their reciprocal monophyly (Lebatha et al. 2006). The Drimiopsis and Resnova species have more loosely packed leaves in the bulb than the species of Ledebouria sensu stricto (Lebatha et al. 2006) and are mostly woodland and forest species as opposed to the open-country Ledebouria (Manning et al. 2004).

Ledebouria marginata, from here.

Some species of Ledebouria have become popular as houseplants, not for their flowers which are reasonably modest, but for their leaves which are fleshy and marked with dark purple blotches and stripes. The number of leaves produced from one bulb at a time varies from up to twenty-five to only a single leaf in Ledebouria monophylla. Mature plants may be up to a metre tall in L. zebrina, down to only 3 mm high in L. galpinii (Venter 1993). The latter (as well L. monophylla) is one of a number of species in which the leaves grow tightly pressed to the ground, so despite the low height of the entire plant, the individual leaves are up to 80 mm long. In such species, the total number of leaves at a time is always low, never more than five. This growth habit is known as geophylly, and the reasons behind it remain uncertain. Geophyllous plants are generally found in areas with strongly seasonal yet regular rainfall (Esler et al. 1999). It has been suggested that the geophyllous habit protects against grazing animals or against CO₂ or water loss; alternatively (as favoured by Esler et al.), it may create a microclimate that affects the temperature of the leaves, either causing their temperature to remain low in the mornings (allowing dew to form on the leaves) and/or raising the temperature of the leaves during midday (allowing elevated rates of photosynthesis).

Leaves of Ledebouria ovatifolia ssp. scabrida, a geophyllous species, photographed by Connall Oosterbroek.

As already alluded to, most Ledebouria plants form flower spikes bearing only pale flowers, though many species may produce more than one spike in succession over a single growing season. Flowers are insect-pollinated by Lepidoptera and Hymenoptera. Fruits are dry capsules, and the seeds are dispersed short distances from the parent plant by wind (generally by being scattered from a waving spike) or water (mostly by falling rain). Some species form lateral bulblets, such as the aptly named Ledebouria socialis (see this page on L. socialis as a house plant), leading to the formation of colonies of plants connected by subterranean stolons up to 200 mm long. The largest recorded such colony, for a clone of L. cooperi, had a diameter of five meeters (Venter 1993).

REFERENCES

Esler, K. J., P. W. Rundel & P. Vorster. 1999. Biogeography of prostrate-leaved geophytes in semi-arid South Africa: hypotheses on functionality. Plant Ecology 142 (1-2): 105-120.

Lebatha, P., M. H. Buys & G. Stedje. 2006. Ledebouria, Resnova and Drimiopsis: a tale of three genera. Taxon 55 (3): 643-652.

Manning, J. C., P. Goldblatt & M. F. Fay. 2004. A revised generic synopsis of Hyacinthaceae in sub-Saharan Africa, based on molecular evidence, including new combinations and the new tribe Pseudoprospereae. Edinburgh Journal of Botany 60 (3): 533-568.

Venter, S. 1993. A revision of the genus Ledebouria Roth in South Africa. MSc thesis, University of Natal.

Peeling the Lily

The toad lily Tricyrtis hirta. Photo by André Karwath.

Pity the poor Liliaceae. At one time, the family stood as the repository for almost all monocots with large-petaled flowers except orchids. Over the years, successive reclassifications have steadily whittled it down until the current Liliaceae is left with a mere ten to sixteen or so genera (depending on whether or not the Calochortaceae are treated as a separate family) found in the Holarctic region. Of course, these genera still include such luminaries as Lilium (lilies) and Tulipa (tulips), so even in its minority the Liliaceae can still draw its share of attention.


Greig's tulip Tulipa greigii growing wild in Kazakhstan. Photo by Rustem Vagapov. I have to admit that the thought of such horticultural wonders as tulips and orchids growing wild has always been a strange one to me.

Molecular studies of the Liliaceae have agreed on the monophyly of Liliaceae sensu stricto (excluding 'Calochortaceae') but differ on the relationships of the 'Calochortaceae', whether a monophyletic sister to Liliaceae s. s. (Patterson & Givnish 2002) or paraphyletic to the latter (Rønsted et al., 2005). Within Liliaceae s. s., there is a well-supported division between the Lilioideae and a small clade Medeoloideae. Whatever the phylogeny, it seems likely that the ancestor of the Liliaceae in the broad sense was a shade-loving, rhizomatous plant with broad reticulate leaves, as is characteristic of Medeoloideae and 'Calochortaceae' other than Calochortus (Patterson & Givnish 2002). Calochortus and Lilioideae independently became adapted to more open habitats, developing narrower leaves and bulbs instead of rhizomes (hence a more seasonal growing cycle). Both lineages also developed more showy flowers than their relatives (showy flowers are also found in the genus Tricyrtis, which may or may not be closely related to Calochortus) and replaced the berries of their ancestors with dehiscent capsules, so that their seeds became dispersed by wind instead of by animals. Again, capsules are also found in Tricyrtis, as well as in the genus Scoliopus that has distinctive fleshy capsules that are believed to encourage seed dispersal by ants (Patterson & Givnish 2002).


The Indian cucumber (because of its edible rhizome) Medeola virginiana, a North American representative of the forest-dwelling Medeloideae. Photo by David Smith.

As well as reproducing by seeds, some Liliaceae also reproduce asexually. A number of bulbiferous species produce bulbils, small lateral offshoots of the bulb. These may break off and grow into new plants elsewhere, generally when carried by the action of burrowing animals such as moles and mole-rats.

REFERENCES

Patterson, T. B., & T. J. Givnish. 2002. Phylogeny, concerted convergence, and phylogenetic niche conservatism in the core Liliales: insights from rbcL and ndhF sequence data. Evolution 56 (2): 233-252.

Rønsted, N., S. Law, H. Thornton, M. F. Fay & M. W. Chase. 2005. Molecular phylogenetic evidence for the monophyly of Fritillaria and Lilium (Liliaceae; Liliales) and the infrageneric classification of Fritillaria. Molecular Phylogenetics and Evolution 35: 509-527.

The Thalli that are Green (Taxon of the Week: Lemnoideae)

The Araceae is the family of plants including such widely-grown species such as calla lilies and taro. Among other things, the family is famous for including some of the largest floral structures in the world. What is perhaps less widely appreciated is that it also includes some of the smallest and also some of the strangest flowering plants of all*.

*The very strangest flowering plants are the Podostemoideae, but I'll save them for another day.


Wolffia arrhiza, one of the world's smallest flowering plants. Each separate dot is an individual plant. Photo by Christian Fischer.

Duckweeds are the minute plant that can be found growing in large numbers on many still bodies of water. The main body of the plant is a flattened, often oval thallus (not a leaf but rather a highly reduced and fused leaf and stem). In three of the recognised genera of duckweeds, Lemna, Spirodela and Landoltia (the 'Lemneae'), one or more short roots emerge from one end of the thallus (the proximal end). In the other two genera, Wolffia and Wolffiella (the Wolffieae), the thallus lack roots. The vascular system is greatly reduced in 'Lemneae' and almost entirely absent in Wolffieae. Much of the thallus is occupied by gas-filled spaces that keep it buoyant (Hillman, 1961). The proximal end of the thallus also bears pockets on the underside from which daughter thalli grow vegetatively or in which the flower develops. The 'Lemneae' possess two such pockets, one on each side, while the Wolffieae possess only a single pocket. The entire plant is generally less than five millimetres (the size reached by Landoltia punctata) while Wolffia individuals are less than half a millimetre long when mature. Phylogenetic analysis indicates that the 'Lemneae' are paraphyletic; Lemna, which is smaller than Spirodela and Landoltia with only a single rooth per thallus, is sister to the even more reduced Wolffieae (Les et al., 2002).


Spirodela (large thalli), Lemna (smaller thalli) and Wolffia (minute thalli). Photo by G. D. Carr.

The flowers of duckweed are correspondingly tiny and many species produce them only rarely with vegetative reproduction being the primary means of multiplication (Hillman, 1961). Daughter thalli may begin producing their own daughters before separating from the parent, leading to the production of small colonies. Individuals of the double-pocketed 'Lemneae' demonstrate 'handedness' in their growth; in a new thallus grown from seed, either the right- or left-hand pocket may be the 'plus' pocket from which the first daughter thallus grows, but all successive vegetatively produced thalli will grow their own first daughter thallus on the same side as their parent did. If a flower is produced (and each individual thallus will only ever flower once) then it will always grow on the other side in the 'minus' pocket. It is a bit of an open (and somewhat academic) question whether duckweeds produce a single hermaphroditic flower or separate male and female flowers, as there are no petals or sepals, but the important detail is that a thallus produces a single pistil and one to three stamens (usually two in 'Lemneae', only ever one in Wolffieae; Wolffieae also only possess a single ovule while 'Lemneae' may possess up to six) which project above the surface of the thallus. The pistil matures before the stamens but may remain receptive until after the stamens open so at least some duckweeds are capable of self-pollination. The exact mode of pollen transport is uncertain: pollen may be carried by wind or water but transport by small insects has also been proposed. Seeds are capable of surviving periods of drying out; many species of duckweed are also capable of producing a dormant form called a turion, a modified, thicker thallus that lacks the air spaces of a normal thallus and possesses a dense load of starch grains instead.


Thick growth of Landoltia punctata. Photo by A. Murray.

Though most authors have regarded them as a separate family, the Lemnaceae, a relationship between duckweeds and Araceae has been popular since the 1800s. The main connecting link has been through comparison with the floating aroid Pistia stratiotes which resembles duckweed both in its general lifestyle and in the production of its flowers in basal pockets. Some authors have even proposed including Pistia in the Lemnaceae and the Palaeocene fossil plant Limnobiophyllum (with reduced floating rosettes) has been suggested as a morphological link between the two (Stockey et al., 1997). Molecular studies, while supporting a nested position for duckweeds within Araceae (which is why I refer to them as subfamily Lemnoideae), have not supported a direct relationship between duckweeds and Pistia (Rothwell et al., 2004); however, duckweeds show much greater branch lengths than other Araceae.

REFERENCES

Hillman, W. S. 1961. The Lemnaceae, or duckweeds: a review of the descriptive and experimental literature. Botanical Review 27 (2): 221-287.

Les, D. H., D. J. Crawford, E. Landolt, J. D. Gabel & R. T. Kimball. 2002. Phylogeny and systematics of Lemnaceae, the duckweed family. Systematic Botany 27 (2): 221-240.

Rothwell, G. W., M. R. Van Atta, H. E. Ballard Jr & R. A. Stockey. 2004. Molecular phylogenetic relationships among Lemnaceae and Araceae using the chloroplast trnL–trnF intergenic spacer. Molecular Phylogenetics and Evolution 30 (2): 378-385.

Stockey, R. A., G. L. Hoffman & G. W. Rothwell. 1997. The fossil monocot Limnobiophyllum scutatum: resolving the phylogeny of Lemnaceae. American Journal of Botany 84 (3): 355-368.

Name the Bug: Pistia stratiotes

Pistia stratiotes. Photo by Bhushan Dalvi.

As two readers correctly surmissed, the main subject of this photo is the aroid Pistia stratiotes, commonly known as water lettuce. While the specimens shown here appear to have become stranded, water lettuce grows as free-floating rosettes on the surface of open bodies of water. The leaves radiate from an extremely shortened central stem with the tiny flowers produced in pockets at the bases of the leaves. As well as producing flowers, water lettuce reproduces vegetatively by the production of lateral stolons that give rise to daughter rosettes. Given time, a colony of water lettuce can carpet an entire lake.

I said that this ID was a clue to the next Taxon of the Week. Pistia stratiotes is not the only floating member of the Araceae: the remaining examples will be the subject of the next post.

Stacks of Barley (Taxon of the Week: Hordeum)

Foxtail barley, Hordeum jubatum, a weedy species found in northern North America and northeast Asia. Photo by Colin Stone.

Hordeum is a genus of thirty or so species (Blattner, 2009, lists 33) whose native range mostly covers Eurasia and the Americas though various species have been spread by humans pretty much throughout the world, either willingly or unwillingly. The most significant of these species from a human perspective is Hordeum vulgare, barley, used in the making of refreshing beverages and the manufacture of eyewear. This is the genus that gave us beer.


Six-rowed barley, Hordeum vulgare, the main cultivated variety of barley. Hordeum species bear single-flowered spikes in groups of three but usually only the central spike develops a seed while the lateral two are abortive. Six-rowed barley has been bred so all three develop seeds. Photo from here.

Hordeum is one of the more basally diverging genera in the grass tribe Triticeae, previously discussed here in relation to the genus Elymus. Unlike many other triticean genera, the concept of Hordeum has remained relatively stable with the exception that some authors have restricted Hordeum to the species H. vulgare and H. bulbosum, placing the other species in a genus Critesion. Blattner (2009) divided the genus into five sections, four monophyletic (sensu Ashlock, at least) sections corresponding to the four genome types found in Hordeum (see the Elymus post for an explanation of the concept of genome types) and an explicitly polyphyletic section Nodosa for species derived from hybrids between species of sections Marina and Stenostachys.


Hare barley, Hordeum murinum ssp. leporinum, native to Europe but widely established around the world. Photo from here.

Hordeum is most diverse in the Americas - 24 species are found naturally in the New World (including two, H. brachyantherum and H. jubatum, that are also native to northeast Asia) with 15 of those native to South America. However, phylogenetic studies show that the genus is in fact Eurasian in origin with all of the New World diploid species belonging to a subclade of a single section (Stenostachys) which probably arrived in North America about four to six million years ago (Blattner, 2009). A number of the polyploid New World species (including both the Bering Strait-straddling species) appear to be derived from hybrids between New World Stenostachys and one of the central Asian Stenostachys species, probably H. roshevitzii - my guess is that they form a tribute to the ability of pollen to be carried amazingly long distances. Also biogeographically interesting are the section Nodosa species, the European H. secalinum and the South African H. capense. Hordeum secalinum appears derived from a cross between the mostly Mediterranean section Marina and a Stenostachys species (the ranges of the two sections overlap in central Asia). Hordeum capense is a biogeographical enigma; geographically isolated from all other species, it carries the same genome combination as H. secalinum (Baum & Johnson, 2003; Blattner, 2009) with which it is morphologically almost identical. Indeed, for a long time H. capense was regarded as a human-introduced population of H. secalinum, probably brought over in the earliest days of European colonisation. However, hybrids between H. secalinum and H. capense are infertile (Baum & Johnson, 2003). Petersen & Seberg (2004) calculated that the genetic divergence between H. secalinum and H. capense was too great for it to be a recent derivative of a human introduction; instead, they felt it must be an older relict that had reached South Africa by means unknown.

REFERENCES

Baum, B. R., & D. A. Johnson. 2003. The South African Hordeum capense is more closely related to some American Hordeum species than to the European Hordeum secalinum: a perspective based on the 5S DNA units (Triticeae: Poaceae). Canadian Journal of Botany 81: 1-11.

Blattner, F. R. 2009. Progress in phylogenetic analysis and a new infrageneric classification of the barley genus Hordeum (Poaceae: Triticeae). Breeding Science 59: 471-480.

Petersen, G., & O. Seberg. 2004. On the origin of the tetraploid species Hordeum capense and H. secalinum (Poaceae). Systematic Botany 29 (4): 862-873.

Scattering the Sheaves (Taxon of the Week: Elymus)

Canada wildrye, Elymus canadensis, a widespread species in North America. Photo by Russ Kleinman & Bill Norris.

Elymus is a cosmopolitan genus of perennial tufted and/or rhizomatous grasses that, depending on the taxonomic treatment used, may include from 20 to 200 species found mostly in cool temperate parts of the world (Quattrocchi, 2006). Bit of a difference between those extremes, you may be thinking? Elymus is part of the Triticeae, the grass tribe that includes wheat, rye and barley. Establishing relationships within the Triticeae has always been a difficult prospect; hybridisation and polyploidy have been major factors in the evolution of the tribe. Until the mid-1980s, most western authors continued to use a classification whose basic philosophy went right back to Linnaeus' Species Plantarum (Barkworth, 2000). This system, in which Elymus contained perennial grasses with 2 or more 2- to 6-flowered spikelets at each node of the rachis (the flower spike), was unashamedly pragmatist and concerned with facilitating species identification rather than describing relationships. A more modern classification had been proposed by a Russian author, Nevski, in the early 1930s but had not been widely accepted outside the communist countries. Among Nevski's most significant changes was the realisation that reduction in the number of flowers at each spikelet to one had occurred multiple times in various genera and his Elymus included species with from one to six flowers.

Starting in the 1940s, an increasing number of cytogenetic studies had established that many of the genera of Triticeae contained chromosomally disparate subgroups that could be identified by the chromosome pairing patterns in hybrids between taxa. A number of authors had integrated some cytogenetic data into revisions of Triticeae but two authors in 1984 independently suggested that Triticeae classification should be based entirely on cytogenetic data alone. Not surprisingly, this lead to a botanical rift - even if one was willing to credit that genetic characters might be a better indication of relationships than morphology (and not everyone was), they were of limited use for field identifications. Before gene sequencing became widely feasible, identifying the cytogenetic nature of a grass required observation of cells undergoing meiotic division. However, genomic data remains a significant factor in Triticeae classification (Barkworth, 2000).


Bottlebrush grass, Elymus hystrix, an inhabitant of the northwest United States from West Virginia to New York. Photo from here.

Each of the genome groups that has been identified in Triticeae has been assigned a letter code: A, B, N, R, etc. Polyploid taxa of hybrid origin may carry chromosomes from more than one genome group; the genus Triticum (wheats), for instance, is characterised as AB (or some further complication thereof, such as AAB). The basic chromosome type of Elymus for North American representatives is StH, representing their descent from one or more hybridisation events between the genera Pseudoroegneria (St) and Hordeum (H; Hordeum includes the barleys) (Mason-Gamer, 2001). Taxa from other parts of the world currently assigned to Elymus all carry the St genome, but may have it combined with different genomes such as Y or W*. Future investigation is required to establish whether these taxa are appropriately placed in Elymus.

*As ploidy level increases, the genome codes for various taxa can get a little hideous. The North American octoploid genus Pascopyrum, for instance, has the genome code StStHHNsNsXX.

Economically speaking, a number of Elymus species are used as pasture grasses for feeding livestock. Quattrocchi (2006) indicates that Elymus grain is usable for food but I haven't found any references to specific species being regularly used as such (apart from indirectly with Elymus species being used in wheat outcrossing). Elymus repens, couch grass, is a particularly tough rhizomatous species that seems to be encouraged in some situations and regarded as a curse in others (many authors refer to couch grass as Elytrigia repens instead but it carries the genome StStH - Barkworth, 2000).

REFERENCES

Barkworth, M. E. 2000. Changing perceptions of the Triticeae. In Grasses: Systematics and Evolution (S. W. L. Jacobs & J. Everett, eds) pp. 110-120. CSIRO: Melbourne.

Mason-Gamer, R. J. 2001. Origin of North American Elymus (Poaceae: Triticeae) allotetraploids based on granule-bound starch synthase gene sequences. Systematic Botany 26 (4): 757-768.

Quattrocchi, U. 2007. CRC World Dictionary of Grasses: common names, scientific names, eponyms, synonyms, and etymology vol. 2. CRC Press.

Taxon of the Week: Rhaphidophora

Rhaphidophora decursiva growing in the Sydney Botanical Gardens. Photo by Tony Rodd.

As currently recognised, Rhaphidophora is a large genus of about 100 species of lianes (woody climbers) of the family Araceae found in the tropics of the Old World from Africa to northern Australia. Rhaphidophora forms part of the tribe Monstereae whose most familiar member is probably Monstera deliciosa, the Swiss cheese plant of many a garden, and the flowers and fruit of Rhaphidophora are similar to those of Monstera. Some Rhaphidophora species have pinnate or perforated leaves while others have entire leaves. Most Rhaphidophora species do not seem to currently have a great deal of economic significance except as ornamental plants though a small number have been investigated in recent years for their pharmacological properties. Rhaphidophora pertusa stems are chopped up and mixed with rice gruel before being fed to cattle or buffaloes in India to induce oestrus (Santosh et al., 2006).


Rhaphidophora foraminifera. Photo by Eric in SF.

The genera of the Monstereae such as Rhaphidophora, Monstera and Epipremnum have not had their definitions substantially revised since 1908 and are currently regarded by many authors as problematic. They have been primarily distinguished on the basis of reproductive anatomy (Rhaphidophora, for instance, has numerous ovules, punctate stigmas and minute albuminous seeds) but reproductive characters are often at odds with vegetative characters (Hay, 1993) and a revision of the group is overdue (matters were not helped by the suggestion - since shown to be mistaken - that Rhaphidophora and Epipremnum shared the same type species). A molecular study by Tam et al. (2004) also identified polyphyly of Rhaphidophora, with the majority of Rhaphidophora species forming a single clade but a significant minority forming clades with species of other genera.

REFERENCES

Hay, A. 1993. Rhaphidophora petrieana - a new aroid liane from tropical Queensland; with a synopsis of the Australian Araceae-Monstereae. Telopea 5 (2): 293-300.

Santosh, C. R., N. B. Shridhar, K. Narayana, S. G. Ramachandra & S. Dinesh. 2006. Studies on the luteolytic, oestrogenic and follicle-stimulating hormone like activity of plant Rhaphidophora pertusa (Roxb.). Journal of Ethnopharmacology 107 (3): 365-369.

Tam, S.-M., P. C. Boyce, T. M. Upson, D. Barabé, A. Bruneau, F. Forest & J. S. Parker. 2004. Intergeneric and infrafamilial phylogeny of subfamily Monsteroideae (Araceae) revealed by chloroplast trnL-F sequences. American Journal of Botany 91 (3): 490-498.

Strangers from Parts Unknown (Taxa of the Week: Juncus section Juncotypus, Juncus amabilis)

Flowerhead of Juncus conglomeratus. If you look closely, you can see the line where the true stem ends, and the elongate stem-like flower bract begins. Photo from Nature Notes from Argyll.

Rushes of the genus Juncus are a large cosmopolitan assemblage of superficially grass-like plants, most commonly found in damp or swampy soils. A number of distinct subgroups are recognisable within the genus, and my subject today is one of those subgroups, the section Juncotypus in the subgenus Agathryon. Most older references will refer to this group as the subgenus or section Genuini, but the precendence of Juncotypus was noted by Kirschner et al. (1999)*. Both names, however, can be translated to give a good idea of what defines this group - section Juncotypus is the "genuine" rushes. Species of this species lack true leaves entirely (the leaves have been reduced to small sheaths at the base of the stem), and instead have clumps of umbranching photosynthetic stalks rising from a basal woody rhizome. The flower clusters appear to born laterally some way down the stalk (Healy & Edgar, 1980; though admittedly, calling the tiny wind-pollinated reproductive organs of rushes "flowers" arguably stretches the term to its limits), but are in fact not - rather, the part of the "stalk" extending past the inflorescence is really the flower bract.

*A few notes for my more zoologically-oriented readers. While zoological nomenclature allows only one formal division between species and genus, the subgenus, botanical nomenclature allows (from highest rank to lowest) subgenus, section, subsection, series and subseries. And while zoological taxonomists tend to be a little chary when it comes to using subgenera, botanical taxonomists have a long history of using every one of those subsidiary ranks to full capacity (some botanists have managed to pluck even further levels out of the ether). Also, while zoological taxonomy interpolates subgeneric names into the full species names (e.g. Brachiosaurus (Giraffatitan) brancai), botanical taxonomy does not - Juncus amabilis is a member of the section Juncotypus, but that doesn't mean that it should be called "Juncus (Juncotypus) amabilis". Finally, while zoological taxonomy regards subgeneric names as distinct entities at the same level of homonymy as generic names (Giraffatitan is nomenclaturally distinct from Brachiosaurus, and because the name has been used for a subgenus, it cannot be used for another genus or subgenus), botanical taxonomy regards the subgeneric name as directly connected to the generic name, so the proper name for today's subject is "Juncus section Juncotypus", not just "Juncotypus". One side-effect of this is that using a name for a subgeneric taxon in one genus does not prevent its use in association with another genus, so (e.g.) Crassula section Glomeratae and Campanula series Glomeratae are not regarded as homonyms.

If you're feeling horribly lost about now, take comfort in my assuring you that, yes, botanical nomenclature really is as horribly complicated as it looks. Personally, I don't understand a word of it.

Species of section Juncotypus are found in temperate habitats over most of the world. Some species are found in tropical latitudes, such as Juncus aemulans in Central America (Mexico to Guatemala) and Juncus decipiens in eastern Asia and New Guines, but at high altitudes (Snogerup et al., 2002; Wilson & Johnson, 2001). More than half the recognised species are found in Australasia, while a few species such as Juncus effusus are found over almost the entire range of the subgenus as either natives or adventives. Some members of the section are notable pasture pests. Though morphologically distinct, recent phylogenetic analyses have not supported the monophyly of the section Juncotypus (Drábková et al., 2006; Drábková & Vlček, 2009). Drábková & Kirschner (2004) particularly commented on the intermediate morphology of Juncus uruguensis between sections Juncotypus and Steirochloa. These results have not yet been incorporated into a taxonomic revision, probably because as yet only a relatively small number of Juncotypus species have been studied in this regard.


Juncus effusus. Photo from here..

Not surprisingly in light of their simple morphology, species of section Juncotypus have mostly been difficult to distinguish. In this regard, I can't do much better than steal wholesale the words of Edgar (1964):

Although the Junci Genuini show obvious differences of habit and colour in the field, these differentiating characters are largely lost in pressing and drying, and herbarium specimens are often difficult to determine. The principal characters which have been used to distinguish the plants are the general size, the presence or absence of lacunae in the pith of the stem, the varying compactness of the inflorescence, the number of stamens, and the relative size of the capsules. Yet none of these characters is wholly satisfactory. For instance, if the general size of the plant is used as a diagnostic character there is an obvious difficulty in placing intermediate sizes. Then, the appearance of the pith in longitudinal section, i.e., whether continuous or interrupted by air spaces, is a very useful feature, but is not constant within some of the species nor, on occasion, even within one plant. Only three species in New Zealand invariably have six stamens and all the others have normally three, though four, five, or even six stamens may be found in occasional flowers. Again, the structure of the inflorescence is constant in some species but extremely variable in others, the flowers are small and inconspicuous and the tepals lose most of their character on drying. Lastly, the ratio between capsule-length and tepal-length which can be a very useful diagnostic character in other groups of Juncus is more difficult to use in this subgenus. In the species with larger capsules it is quite reliable, but in the species with the smallest flowers the difference in length between capsule and tepals is rarely greater than 0.5 mm and usually very much less, so that the ratio between the lengths does not make a convenient diagnostic character.

Diagnostic features of Juncus amabilis. Images from here.

When she made this complaint, Edgar (1964) was reviewing the New Zealand species of "Juncus genuini". In that paper, she described a new species Juncus amabilis, which was distinguished by its small size, extremely dark red-purple basal sheaths and pointed capsules that were distinctly longer than the tepals. Juncus amabilis has a distinctly scattered distribution in New Zealand, with specimens recorded from Auckland, Waikato, the Bay of Plenty, southern Canterbury and Otago (for those unfamiliar with New Zealand geography, that leaves a big gap across the southern North Island and northern South Island without records).

It wasn't until later that the reason for this unusual distribution pattern became clear, when Juncus amabilis was also identified in damp wastelands (primarily along river edges) in southern Australia. It now appears likely that, in spite of where it was initially discovered, J. amabilis is not a native of New Zealand, but an introduction from Australia*. Within Australia, the distribution of J. amabilis remains scattered (a map can be seen here) but, while uncommon, the species does not seem to be regarded as particularly endangered. It looks as if habitat availability rather than human impact may be the cause of its rarity.

*This is unusual, but not unique. A number of organisms have been described as introductions before being recorded from their native ranges. Among harvestmen, for instance, the species Ibantila cubana was originally described (as the species name indicates) from Cuba. However, I. cubana is the only species of the Old World family Podoctidae recorded from the Americas and was collected in a botanical garden, so it is almost certainly an exotic (Kury, 2003). The original homeland of this species remains as yet unknown.

REFERENCES

Drábková, L., J. Kirschner & Č. Vlček. 2006. Phylogenetic relationships within Luzula DC. and Juncus L. (Juncaceae): a comparison of phylogenetic signals of trnL-trnF intergenic spacer, trnL intron and rbcL plastome sequence data. Cladistics 22 (2): 132-143.

Drábková, L., & J. Kirschner. 2004. Juncus uruguensis - a member of the section Juncotypus (Juncaceae, Juncus subg. Agathryon). Nordic Journal of Botany 22: 687-691.

Drábková, L. Z., & Č. Vlček. 2009. DNA variation within Juncaceae: comparison of impact of organelle regions on phylogeny. Plant Systematics and Evolution 278: 169-186.

Edgar, E. 1964. The leafless species of Juncus in New Zealand. New Zealand Journal of Botany 2: 177-204.

Healy, A. J., & E. Edgar. 1980. Flora of New Zealand vol. III. Adventive cyperaceous, petalous and spathaceous monocotyledons. P. D. Hasselberg, Government Printer: Wellington (New Zealand).

Kirschner, J., L. J. Novara, V. S. Novikov, S. Snogerup & Z. Kaplan. 1999. Supraspecific division of the genus Juncus (Juncaceae). Folia Geobotanica 34 (3): 377-390.

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachnida, Opiliones). Revista Ibérica de Aracnología, special monographic volume 1: 1-337.

Snogerup, S., P. F. Zika & J. Kirschner. 2002. Taxonomic and nomenclatural notes on Juncus. Preslia 74: 247-266.

Wilson, K. L., & L. A. S. Johnson. 2001. The genus Juncus (Juncaceae) in Malesia and allied septate-leaved species in adjoining regions. Telopea 9 (2): 357-397.