72 OPIII^E.E. Chap II. 



Howei'8, and the strong- sweet odour emitted by them at 

 night, all show that this plant depends for its fertilisa- 

 tion on the larger nocturnal Lepidoptera. I have 

 often found spikes with almost all the pollinia removed. 

 From the lateral position and distance of the two 

 viscid discs from each other, the same moth would 

 generally remove only one pollinium at a time ; and 

 in a spike which had not as yet been much visited, 

 three flowers had both jDollinia, and eight flowers had 

 only one pollinium removed. From the position of 

 the discs it might have been anticipated that they 

 would adhere to the side of the head or fjice of moths ; 

 and Mr. F. Bond sent me a specimen of Hadena dentina 

 with one eye covered and blinded by a disc, and a 

 specimen of Plusia v. aureum with a disc attached to 

 the edge of the eye. Mr. Marshall* collected twenty 

 specimens of Cucidlia wnibratica on an island in Der- 

 wentwater, separated by half-a-mile of water from anv 

 spot where H. chlorantha grew ; nevertheless, seven of 

 these moths had the pollinia of this Orchid aflixed to 

 their eyes. Although the discs are so adhesive that 

 almost all the pollinia in a bunch of flowers which was 

 carried in my hand and thus shaken were removed 

 by adhering to the petals or sepals, yet it is certain 

 that motlis, probably the smaller species, often visit 

 these flowers without removing the pollinia; for on 

 examining the discs of a large number of pollinia 

 whilst still in their cells I found minute Lepido- 

 pterous scales glued to them. 



The cause of the flowers of various kinds of Orchids 

 being constructed so that the pollinia are always 

 affixed to the eyes or proboscides of Lepidoptera, and 

 to the naked foreheads or proboscides of Hymenoptera, 



* ' Nature,' Sept. 12, 1S72, p. 398. 



