154 Mr. C. Darwin on the Fertilization of Orchids. 



inhabiting South Brazil. I much regret that I have not here 

 space or time to give an abstract of his many discoveries, 

 which support the general conclusions given in my work; 

 but I hope that he will some day be induced to publish a full 

 account of his observations. 



Fertilization of Catasetum (p. 211). — It has been highly 

 satisfactory to me that my observations and predictive conclu- 

 sions in regard to Catasetum have been fully confirmed by the 

 late Dr. Criiger, the Director of the Botanic Gardens of Tri- 

 nidad, in letters to me and in his paper in the ' Journal of the 

 Linnean Society' (vol. viii. Bot. 1864, p. 127). He sent me 

 specimens of the bees, belonging to three species of Euglossa, 

 which he saw gnawing the inside of the labellum. The pol- 

 linia, when ejected, become attached to, and lie flat on, the 

 backs of the bees, on the hairy surface of the thorax. Dr. 

 Criiger has also proved that I was correct in asserting that 

 the sexes of Catasetum are separate, for he fertilized female 

 flowers with pollen from the male plants ; and Fritz Miiller 

 effected the same thing with Catasetum mentosum in South 

 Brazil. Nevertheless, from two accounts which I have re- 

 ceived, it appears that Catasetum tridentatum^ though a male 

 plant, occasionally produces seed-capsules ; but every botanist 

 knows that this occasionally occurs with the males of other 

 dioecious plants. Fritz Miiller has given (Botanische Zeitung, 

 Sept. 1868, p. 630) a most interesting account, agreeing with 

 mine, of the state of the minute pollinia in the female plant : 

 the anther never opens, and the pollen-masses are not attached 

 to the viscid disks, so that they cannot be removed by any 

 natural means. The pollen-grains, as so generally occm's with 

 rudimentary organs, are extremely variable in size and shape. 

 Nevertheless the grains of the rudimentary pollen-masses be- 

 longing to the female plant, when applied (which can never 

 naturally occur) to the stigmatic surface, emitted their pollen- 

 tubes ! This appears to me a very curious instance of the 

 slow and gradual manner in which structures are modified ; 

 for the female pollen-masses, included within an anther which 

 never opens, are seen still partially to retain their former 

 powers and function. 



Mormodes luxatum (p. 265). — I have now examined another 

 species of Mormodes^ the rare M. luxatum^ and I find that the 

 chief points of structure, and the action of the different parts, 

 including the sensitiveness of the filament, are the same as 

 in M. ignea. The cup of the labellum, however, is much 

 larger, and is not pressed down firmly on the filament on the 

 summit of the column. This cup probably serves to attract 

 insects, and, as in (kitasetwn^ is gnawed by them. • ^J'lio flowers 



