March 10, 2009 3 Comments
Finally, I present to you the answers to “Winter botany quiz #2 “. The delay in providing these answers was two-fold. Firstly, I knew this would be a hard test, so I wanted to give people plenty of time to figure out the answers. Secondly, the answers were delayed an extra day due because of some debate that arose among the experts I consulted about #3 – more on that below. I thank all those who participated, and while there was no clear-cut “winner”, several honorable mentions are deserved:
- Doug Taron, who was the first to properly deduce the South African nature of these plants.
- James C. Trager, a myrmecologist (yet still my friend!) who correctly identified the genus of #1.
- Everyone, for guessing that #2 was “an orchid” – although Tom @ Ohio Nature was the only one to use the formal scientific name for the family, and Doug Taron was the only one to attempt a generic identification (and came close – Oncidium and Ansellia are both assigned to the tribe Cymbidieae in the subfamily Epidendroideae).
#1. Ornithogalum seineri (family Hyacinthaceae)
Ornithogalum is a large genus occurring mostly in the drier habitats of southern Africa and around the Mediterranean. The genus and its relatives were formerly included in the Liliaceae (as many of the participants guessed), but the group is now given familial status as the Hyacinthaceae. This genus contains numerous species of horticultural note. One is (as James noted) O. umbellatum, or “star of Bethlehem”, which in North America has escaped cultivation as a garden ornamental and gained status as an invasive weed. Another is O. longibracteatum (syn. caudatum), a popular houseplant with the common name “pregnant onion”. This species, native to the Cape and Natal Provinces of South Africa, is easily recognized by its bulb that “gives birth” to tiny replicas of itself just beneath a thin, transparent ‘onion’ skin (as shown in the photo at right from Trans-Pacific Nursery). At flowering, a long spike grows from the center of the green strap leaves, eventually giving rise to a spearhead of tiny white flowers situated at the end.
While I couldn’t find much information about O. seineri, I did find this spectacular photo of numerous blooming plants in bushveld habitat amongst grazing zebra (photo by ingrid1968 in this post at SANParks.org Forum). My view of this species was not quite so spectacular, as I saw only the lone plant in the photographs posted earlier.
#2. Ansellia africana (family Orchidaceae)
Ansellia is an African genus of orchid commonly called Leopard Orchid or African Ansellia. There is some degree of morphological, geographical and ecological variation in Ansellia populations, with the result that several species, subspecies and varieties have been described. Flower color varies from pure yellow to variably splotched with brown to almost completely black with finely indicated yellow divisions. Recent taxonomic work has concluded that there are no discontinuities within the spectra of variations exhibited and the populations are thus attributable to the single, polytopic species, A. africana (Khayota 1999).
Ansellia africana is a large, perennial, epiphytic species that usually grows attached to the branches of tall trees but is sometimes found growing on rocks. This genus is immediately recognizable by its large, cane-like pseudobulbs that arise from a basal rhizome and is notable for the white, needle-like, upward pointing aerial roots that form a sort of “trash basket” around the clump. The term is surprisingly appropriate, since the root basket seems to function in catching dropping leaves, flowers and detritus which provide nutrients for the plant as they decay. This species can grow to enormous size and often forms spectacular clumps, some of which have an estimated weight of more than one ton.
Of the three plants featured in the quiz, this was the one I expected someone would guess, since the species is popularly cultivated by orchid enthusiasts. Unfortunately, the pressures of wild collection for commercial purposes has caused declines in its population. The problem is exacerbated by the unsustainable methods use to harvest, transport, and cultivate wild-born plants. Host trees are usually cut down and sections with the orchid removed, resulting in wholesale destruction of both orchids and hosts. After harvesting, plants are cut up and transported slowly in open handcarts, to be sold along roadsides where they may sit exposed to full sun for days or weeks. Cutting the clumps damages the roots, and exposure results in dessication, making it difficult for harvested plants to recover once in cultivation. Plants that do survive harvest and transplant suffer high mortality rates in cultivation due to improper attention to light and moisture regimes.
#3. Adenia sp., poss. glauca (family Passifloraceae)
To be completely honest, not only did I not expect anyone to guess this one, I didn’t think I was even going to be able to provide an answer. I sent the photos to my friend and colleague, George Yatskievych, director of the Flora of Missouri Project (and author of the recently published Steyermark’s Flora of Missouri, 1999 and 2006), who forwarded the photographs to several more colleagues, and at the same time I posted the photos on SANParks.org Forum (a fantastic resource, which I just recently discovered myself, for those interested in South Africa National Parks and their natural history). It took some time for these sources to weigh in with their opinion, which in the end were in agreement that it represented a species of African passion flower in the genus Adenia of the family Passifloraceae (not to be confused with Adenium, a genus of flowering plants in the family Apocynaceae – also occurring in Africa). As for which species, the choices had been narrowed down to either A. glauca or A. fruticosa. According to Imberbe, a photo of the leaves would have been diagnostic, and the flowers are also different (A. glauca has yellow flowers while those of A. fruticosa are green). Fred Dortort, in an article on the University of California at Berkely Botanical Garden website titled, “Passion and Poison“, notes that A. fruticosa has a tall, spindle-shaped caudex topped with a few thin, sparsely-leafed, arching branches, while in A. glauca the caudex is roughly globose and can become quite large. This description seems to favor A. glauca, which Imberbe also noted was known to occur in the area where I took the photographs.
Species identification aside, the genus Adenia is notable for its bizarre adaptations for water storage. Most of the 100 or so species in this Afrotropical and Indomalaysian genus have underground tubers. Those of species adapted to drier environments have grown proportionately larger, with some turning into above ground caudices that can take several different forms and that, in some species, may reach up to eight feet in diameter and height. Even more notable than these succulent adaptations are the poisonous properties that many plants in the genus possess. Not all species have been analyzed (and I found little or conflicting information about A. glauca and A. fruticosa), but one species in the genus – A. digitata – has gained notoriety as perhaps the most poisonous plant in the world. Two different toxins are found within its tuber, one a cyanogenic glycoside, the other a particularly potent toxin called modeccin. The latter is a 57kD protein that resembles ricin and acts a powerful inhibitor of protein synthesis by binding to ribosomes (Gasperi-Campani et al. 1978). Imberbe, in her comments about the photos I posted on SANParks.org Forum, noted the following about plants in this group:
…take heed of the Afrikaans name “Bobbejaangif” (Baboon poison)… It has been used as a fish poison, as well as in suicide and murder. It causes nausea, fits and liver and kidney damage.
Gasperi-Campani, A., L. Barbieri, E. Lorenzoni, L. Montanaro, S. Sperti, E. Bonetti, & F. Stirpe. 1978. Modeccin, the toxin of Adenia digitata. Biochemistry Journal 174:491-496.
Khayota, B. N. 1999. Notes on systematics, ecology and conservation of Ansellia (Orchidaceae), pp. 423-425. In: J. Timberlake & S. Kativu (eds.), African Plants: Biodiversity, Taxonomy and Uses, Royal Botanic Gardens, Kew.
Copyright © Ted C. MacRae 2009