Mr. C. Darwin on the Fertilization of Orchids. 157 



beset with minute, rigid, sharp-pointed papillae, all directed 

 forwards, which are excellently adapted to brush off the pollen 

 from an insect's liead or back." 



The use of tlie copious fuid contained within the laheJhan 

 o/ Coryanthes {p. 278). — The Coryanthes macrantha is per- 

 haps the most wonderful of all known orchids, even more 

 wonderful in structure and function than Catasetum. Its 

 manner of fertilization has been described by Dr. Criiger in 

 the 'Journal of the Linnean Society' (vol. viii. Bot. 1864, 

 p. 130) , and in letters to me. He sent me bees, belonging to 

 the genus Euqlossa, which he saw at work. The fluid in the 

 bucket formed by the basal part of the labellum is not nectar 

 and does not attract insects, but serves, by wetting their 

 wings, to prevent them from crawling out except through the 

 small passages close to the anther and stigma. Thus the 

 secretion of fluid in this orchis serves exactly the same end as 

 the inflected margins of the lal)cllum in Cyprijjedium. 



On the evidence that Insects visit many exotic Orchids in order 

 to gnaio jycirts of the laMIum, and not for the sake of nectar 

 (p. 284). — It has been highly satisfactory to me tliat this hypo- 

 thesis has been fully confirmed. In the West Indies, Dr. Criiger 

 witnessed humble-bees of the genus Euglossa gnawing the 

 labellum of Catasetum^ Coryanthes^ Gongora^ and Stanhopea ; 

 and Fritz Miiller has repeatedly found, in South Brazil, tiie 

 prominences on the labellum of Oncidium gnawed. We are 

 thus enabled to understand the meaning of the various extra- 

 ordinary crests and projections on the labellum of various 

 exotic orchids ; for they invariably stand in such a position 

 that insects, whilst gnawing them, will be almost sm-e to 

 touch the viscid disks of the pollinia, and thus remove them. 



Bonatea sjjeciosa (p. 305). — The manner of fertilization of 

 this extraordinary orchis has now been fidly described by !Mr. 

 E. Trimcn in the ' Journal of the Linnean Society ' (vol. ix. 

 Bot. 1865, p. 156). A projection rising from the base of the 

 labellum is one of its most remarkable peculiarities, as an in- 

 sect is thus compelled to insert its proboscis on one side, and 

 thus to touch one of the two widely separated and projecting 

 viscid disks. Mr. J. P. Mansel Weale has also published 

 {ibid. vol. x. 1869, p. 470) analogous observations on a second 

 species, viz. Bo)iatea Banciuii. Mr. Weale caught a ski])])er- 

 butterriy {Pyrgus ehno) quite embarrassed by the number of 

 pollinia belonging to this orchis which adhered to its sternum. 

 I do not know of any other case in which the pollinia adhere 

 to the sternum of a Lepidopterous insect. 



On the nature of the contraction irhich causes the jwUinia, 

 after their removal from the anther, to change their position 

 ' Ann.&Mag.N.IIist. Scr. 4. Vol.'w. 12 



