158 THE ORIGIN OF SPECIES 



tacles, with the stamens and pistils modified in many ways, some- 

 times forming trap-like contrivances, and sometimes 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 ingenious man, if he had not witnessed what 

 takes place, could never have imagined what purpose all these 

 parts serve. But Dr. Croger saw crowds of large humble-bees visit- 

 ing the gigantic flowers of this orchid, not in order to suck nectar, 

 but to gnaw off the ridges within the chamber above the bucket; 

 in doing this they frequently pushed each other into the bucket, 

 and their wings being thus wetted they could not fly away, but 

 were compelled to crawl out through the passage formed by the 

 spout or overflow. Dr. Criiger saw a "continual procession" of 

 bees thus crawling out of their involuntary bath. The passage is 

 narrow, and is roofed over by the column, so that a bee, in forcing 

 its way out, first rubs its back against the viscid stigma and then 

 against the viscid glands of the pollen-masses. The pollen-masses 

 are thus glued to the back of the bee which first happens to crawl 

 out through the passage of a lately expanded flower, and are thus 

 carried away. Dr. Criiger sent me a flower in spirits of wine, with 

 a bee which he had killed before it had quite crawled out, with a 

 pollen-mass still fastened to its back. When the bee, thus pro- 

 vided, flies to another flower, or to the same flower a second time, 

 and is pushed by its comrades into the bucket and then crawls out 

 by the passage, the pollen-mass necessarily comes first into con- 

 tact with the viscid stigma, and adheres to it, and the flower is 

 fertilized. Now, at last we see the full use of every part of the 

 flower, of the water-secreting horns of the bucket half-full of 

 water, which prevents the bees from flying away, and forces them 

 to crawl out through the spout, and rub against the properly placed 

 viscid pollen-masses and the viscid stigma. 



The construction of the flower in another closely allied orchid, 

 namely, the Catasetum, is widely different, though serving the 

 same end; and is equally curious. Bees visit these flowers, like 

 those of the Coryanthes, in order to gnaw the labellum; in doing 



