Mr. C. Darwin on the Fertilization of Orchids. 155 



are asymmetrical to an extraordinary degree, the right-hand 

 and left-hand sides differing much in shape. 



Cycnoches ventricosum (p. 265). — The plant described in my 

 work as a second species of Mormodes proves to be Cycnoches 

 ventricosum. I first received from Mr. Veitch some flower-buds, 

 from which the section (fig. xxx.) was taken ; but subsequently 

 he sent me some perfect flowers. The yellowish-green petals 

 and sepals are reflexed ; the thick labellum is singularly shaped, 

 with its upper surface convex, like a shallow basin turned 

 upside down. The thin column is of extraordinary length, and 

 arches like the neck of a swan over the labellum ; so that the 

 whole flower presents a very singular appearance. In the sec- 

 tion of the flower, given in my work, we see the elastic pedicel 

 of the pollinium bowed, as in Catasetum or Mormodes ; but at 

 the period of growth represented in the figure the pedicel was 

 still united to the rostellum, the future line of separation being 

 shown by a layer of hyaline tissue indistinct towards the upper 

 end of the disk. The disk is of gigantic size, and its lower 

 end is produced into a great fringed curtain, which hangs in 

 front of the stigmatic chamber. The viscid matter of the disk 

 sets hard very quickly, and changes colour. The disk ad- 

 heres to any object with surprising strength. The anther is 

 very different in shape from that of Catasetum or Mormodes^ 

 and apparently would retain the pollen-masses with greater 

 force. A part of the filament of the anther, lying between 

 two little leaf-like appendages, is sensitive ; and when this 

 part is touched, the pollinium is swung upwards, as in Mor- 

 modes^ and with sufficient force, if no object stands in the 

 way, to throw it to the distance of an inch. An insect of 

 large size alights probably on the labellum, for the sake of 

 gnawing the convex surface, or perhaps on the extremity of 

 the arched and depending column, and then, by touching the 

 sensitive point, causes the ejection of the pollen-masses, which 

 are affixed to its body and thus transported to another flower 

 or plant. 



Fertilization of the Arethusege (p. 269). — Epipogium Gmelini 

 has been the subject of an admirable memoir (Ueber den Blii- 

 thenbau, &c., Gottingen, 1866) by Dr. P. Rohrbach, who 

 has shown how the flowers are fertilized by Bombus lucorum. 

 With respect to another genus belonging to this same tribe, 

 namely Pogonia^ Dr. Scudder of the United States has de- 

 scribed (Proc. Boston Nat. Hist. Soc. vol. ix. 1863, p. 182) 

 the manner in which it is fertilized by the aid of insects. 



Cypripedium (p. 274). — Prof. Asa Gray, after examining 

 several American species of Cyjyrijyedium, wrote to me (see 

 also Amer. Journ. of Science, vol. xxxiv. 1862, p. 427) that 



