LETTER 608. TO JOHN LINDLEY.

(608/1. In the following fragment occurs the earliest mention of Darwin's work on the three sexual forms of Catasetum tridentatum. Sir R. Schomburgk (608/2. "Trans. Linn. Soc." XVII., page 522.) described Catasetum tridentatum, Monacanthus viridis and Myanthus barbatus occurring on a single plant, but it remained for Darwin to make out that they are the male, female and hermaphrodite forms of a single species. (608/3. "Fertilisation of Orchids," Edition I., page 236; Edition II., page 196.)

With regard to the species of Acropera (Gongora) (608/4. Acropera Loddigesii = Gongora galeata: A. luteola = G. fusca ("Index Kewensis").) he was wrong in his surmise. The apparent sterility seems to be explicable by Hildebrand's discovery (608/5. "Bot. Zeitung," 1863 and 1865.) that in some orchids the ovules are not developed until pollinisation has occurred. (608/6. "Fertilisation of Orchids," Edition II., page 172. See Letter 633.))

Down, December 15th [1861].

I am so nearly ready for press that I will not ask for anything more; unless, indeed, you stumbled on Mormodes in flower. As I am writing I will just mention that I am convinced from the rudimentary state of the ovules, and from the state of the stigma, that the whole plant of Acropera luteola (and I believe A. Loddigesii) is male. Have you ever seen any form from the same countries which could be the females? Of course no answer is expected unless you have ever observed anything to bear on this. I may add [judging from the] state of the ovules and of the pollen [that]:--

Catasetum tridentatum is male (and never seeds, according to Schomburgk, whom you have accidentally misquoted in the "Vegetable Kingdom"). Monacanthus viridis is female. Myanthus barbatus is the hermaphrodite form of same species.