41 6 History of the Sexual Theory. [BOOK in. 



by the study of structural relations in flowers, which were 

 apparently trivial and open to the eyes of all men, first arrived 

 at ideas which in the course of a few years were to lead to such 

 far-reaching results. He says : 'In the summer of 1787 I was 

 attentively examining the flowers of Geranium sylvaticum, and 

 observed that the lower part of the petals was provided with 

 slender rough hairs on the inside and on both edges. Con- 

 vinced that the wise framer of nature has not produced a single 

 hair without a definite purpose, I considered what end these 

 hairs might be intended to serve. And it soon occurred to 

 me, that on the supposition that the five drops of juice which 

 are secreted by the same number of glands are intended for 

 the food of certain insects, it is not unlikely that there is some 

 provision for protecting this juice from being spoiled by rain, 

 and that the hairs might have been placed where they are for 

 this purpose. Since the flower is upright, and tolerably large, 

 drops of rain must fall into it when it rains. But no drop of 

 rain can reach one of the drops of juice and mix with it, 

 because it is stopped by the hairs, which are over the juice- 

 drops, just as a drop of sweat falling down a man's brow is 

 stopped by the eye-brow and eye-lash, and hindered from 

 running into the eye. An insect is not hindered by these hairs 

 from getting at the drops of juice. I examined other flowers 

 and found that several of them had something in their structure, 

 which seemed exactly to serve this end. The longer I con- 

 tinued this investigation, the more I saw that flowers which 

 contain this kind of juice are so contrived, that insects can 

 easily reach it, but that the rain cannot spoil it ; but I gathered 

 from this that it is for the sake of the insects that these flowers 

 secrete the juice, and that it is secured against rain that they 

 may be able to enjoy it pure and unspoilt.' Next year, following 

 out an idea suggested by the flowers of Myosotis palustris, he 

 found that the position of spots of different colours on the 

 corolla have some connection with the place where the juice is 

 secreted, and with the same ready reasoning as before he came 



