2 IMPORTANCE OF INSECTS [chap. 



been modified in a similar manner : the observations 

 of botanists, especially of Sprengel, Darwin, and H. 

 Muller, have shown that the forms and colours of 

 wild flowers are mainly owing to the unconscious 

 selection exercised by insects, although no doubt the 

 existence of a certain amount of colouring matter 

 is, as we see in the autumn tints, in various fungi, 

 seaweeds, &c., due to other causes. 



Sprengel appears to have been the first who per- 

 ceived the intimate relations which exist between 

 plants and insects ; and Geranium sylvaticum (see p. i) 

 will always have an interest as being the flower which 

 first led him to his researches. In the year 1787 he 

 observed that in the corolla of this species there are 

 a number of delicate hairs ; and, convinced, as he says, . 

 that "the wise Author of Nature would not have 

 created even a hair in vain," he endeavoured to ascer- 

 tain the use of these hairs, and satisfied himself that 

 they served to protect the honey from rain. 



His attention having thus been drawn to the sub- 

 ject, he examined numerous other flowers with great 

 care, and was surprised to find how many points in 

 reference to them could be explained by their rela- 

 tions to insects. 



The visits of insects are of great importance to 

 plants in transferring the pollen from the stamens to 

 the pistil. In many plants the stamens and pistil are 

 situated in separate flowers : and even in those cases 

 where they are contained in the same flower, self-fer- 

 tilisation is often rendered difficult, or impossible; 

 sometimes by the felative position oF the stamens and 

 pistil, sometimes by their not coming to maturity at 



