280 BOTANY [CHAP. X 



Letter 607 You must be very busy with your change of residence ; 

 but when you are settled and have some leisure, perhaps you 

 will be so kind as to give me some cases of dimorphism, like 

 that of -Primula. Should you object to my adding them to 

 those given me by A. Gray ? By the way, I heard from 

 A. Gray this morning, and he gives me two very curious 

 cases in Boragineae. 



Letter 608 To John Lindley. 



In the following fragment occurs the earliest mention of Darwin's 

 work on the three sexual forms of Catasetum tridentatum. Sir R. 

 Schomburgk 1 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. 2 



With regard to the species of Acropera (Gongora) 3 he was wrong in 

 his surmise. The apparent sterility seems to be explicable by Hilde- 

 brand's 4 discovery that in some orchids the ovules are not developed 

 until pollinisation has occurred. 5 



Down, Dec. I5th [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. Loddigesif) 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}. Monacantlius viridis is female. 

 Myanthus barbatus is the hermaphrodite form of same 

 species. 



1 Trans. Linn. Soc., XVII., p. 522. 



2 Fertilisation of Orchids, Ed. I., p. 236 ; Ed. II., p. 196. 



3 Acropera Loddigesii Gongora galeata : A. luteola=G.fusca (Index 

 Kewensis}. 



4 Bot. Zeitung, 1863 and 1865. 



5 Fertilisation of Orchids, Ed. II., p. 172. See Letter 633. 



