CHAP. X. SEXUAL RELATIONS OF PLANTS. 409 



pollen of anemophilous plants are no doubt both 

 necessary, as their pollen has generally to be carried 

 to the stigmas of other and often distant flowers ; for, 

 as we shall soon see, most anemophilous plants have 

 their sexes separated. The fertilisation of these plants 

 is generally aided by the stigmas being of large 

 size or plumose ; and in the case of the Coniferse, 

 by the naked ovules secreting a drop of fluid, as 

 shown by Delpino. Although the number of ane- 

 mophilous species is small, as the author just quoted 

 remarks, the number of individuals is large in com- 

 parison with that of entomophilous species. This 

 holds good especially in cold and temperate regions, 

 where insects are not so numerous as under a warmer 

 climate, and where consequently entomophilous plants 

 are less favourably situated. We see this in our 

 forests of Coniferse and other trees, such as oaks, 

 beeches, birches, ashes, &c. ; and in the Gramineae, 

 Cyperaceae, and Juncaceaa, which clothe our meadows 

 and swamps ; all these trees and plants being fertilised 

 by the wind. As a large quantity of pollen is wasted 

 by anemophilous plants, it is surprising that so many 

 vigorous species of this kind abounding with individuals 

 should still exist in any part of the world ; for if they 

 had been rendered entomophilous, their pollen would 

 have been transported by the aid of the senses and 

 appetites of insects with incomparably greater safety 

 than by the wind. That such a conversion is possible 

 can hardly be doubted, from the remarks lately made 

 on the existence of intermediate forms; and apparently 

 it has been effected in the group of willows, as we may 

 infer from the nature of their nearest allies.* 



It seems at first sight a still more surprising fact 



* H. Muller, 'Die Befruchtung,' &c. p. 149. 



