Darwin and Catasetum
Here's a historical puzzle that I'm hoping someone familiar with the genus Catasetum can help to sort out. In 1862, Charles Darwin published a paper in the Journal of the Linnean Society called "On the Three remarkable Sexual Forms of Catasetum tridentatum" in which he described three orchids identified (at that time) as belonging to three different genera and concluded that they were male, hermaphroditic (perfect), and female flowers of one species. The full paper is available online; unfortunately, I can't find a link shorter than the 25 character limit, but if you Google the title of the paper, it should be one of the first results. I have attached the drawings that appeared in Darwin's paper of the three flowers.
The issue had been brought to Darwin's attention when someone reported finding all three flowers growing on one plant. Darwin examined flowers preserved in spirits, but not from the plant that produced all three forms; if I'm reading the paper correctly, he examined (using the names of the time) a single flower from Catasetum tridentatum and flowers of Myanthus barbatus and Monachanthus viridis that occurred together on one plant. He concluded that they were all C. tridentatum, and that the C. tridentatum flower he examined was male, the Myanthus barbatus flower was perfect, and the Monachanthus viridis flower was female. The question is, what are the modern names of the plants he examined?
According to Wikipedia (never authoritative, I know, but I don't have anything more authoritative to go on), Catasetum macrocarpum is synonymous with C. tridentatum and Monachanthus viridis (in various incarnations), but not Myanthus barbatus. Still according to Wikipedia, C. barbatum is synonymous with Myanthus barbatus and other incarnations of Monachanthus viridis. Using Google images, it is easy enough to find photos of male and female flowers of C. macrocarpum and C. barbatum, but I do not find any photos of C. macrocarpum that resemble the distinctive male C. barbatum (the bearded form that gives it its name), nor do I find photos of C. barbatum that resemble the male C. macrocarpum. The females of both species do look very similar, and it's easy to imagine how they could be confused for each other, particularly when preserved in spirits.
From all of this, I am guessing that the flowers Darwin examined were a male C. macrocarpum (his C. tridentatum) and a male and female C. barbatum (his Myanthus and Monachanthus). This theory, however, fails to explain the reports of all three flower types occurring on one plant.
In my efforts to resolve this puzzle, I've found a more recent paper reporting plants in the genus Catasetum that produce three types of flowers:
Gustavo A. Romero, 1992. Non-functional flowers in Catasetum orchids. Botanical Journal of the Linnean Society. 109 (2): 305-313.
Unfortunately, I only have access to the abstract, not the full paper, but from reading the abstract, it would seem that the flowers that are neither male nor female types are intermediate in form, not completely different forms. It's hard to imagine anyone describing a male barbatum-type flower as intermediate between the male and female forms of C. macrocarpum, or a male macrocarpum-type flower as intermediate between the male and female forms of C. barbatum.
Is there any chance, then, that the flowers Darwin examined all belonged to one species? Are there reliable modern reports of all three types of flowers (one resembling C. macrocarpum male, one resembling C. barbatum male, and one resembling a female of either species) occurring on one plant?
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