Chap. VI.] OF NATUKAL SELECTION. 241 



but such a view of nature is incredible. With plants 

 having separated sexes, and with those in which, though 

 hermaphrodites, the pollen does not spontaneously fall 

 on the stigma, some aid is necessary for their fertilisa- 

 tion. With several kinds this is effected by the 

 pollen-grains, which are light and incoherent, being 

 blown by the wind through mere chance on to the 

 stigma ; and this is the simplest plan which can well 

 be conceived. An almost equally simple, though very 

 different, plan occurs in many plants in which a 

 symmetrical flower secretes a few drops of nectar, and 

 is consequently visited by insects ; and these carry the 

 pollen from the anthers to the stigma. 



From this simple stage we may pass through an 

 inexhaustible number of contrivances, all for the same 

 purpose and effected in essentially the same manner, 

 but entailing changes in every part of the flower. The 

 nectar may be stored in variously shaped receptacles, 

 with the stamens and pistils modified in many ways, 

 sometimes forming trap-like contrivances, and some- 

 times capable of neatly adapted movements through 

 irritability or elasticity. From such structures we may 

 advance till we come to such a case of extraordinary 

 adaptation as that lately described by Dr. Criiger in 

 the Coryanthes. This orchid has part of its labellum 

 or lower lip hollowed out into a great bucket, into 

 which drops of almost pure water continually fall from 

 two secreting horns which stand above it; and when 

 the bucket is half full, the water overflows by a spout 

 on one side. The basal part of the labellum stands 

 over the bucket, and is itself hollowed out into a sort 

 of chamber with two lateral entrances ; within this 

 chamber there are curious fleshy ridges. The most 



