THE WIND AS CAKKIEK. 141 



other plant that grows close by them. As soon 

 as they have begun to set their seeds the 

 stigmas wither, and then the male flowers open 

 in a bright yellow mass, the stalks of their 

 stamens lengthening out as they do so, and 

 allowing the wind to carry the pollen freely. 

 Here, although the males are above, the pecu- 

 liar arrangement by which the females ripen 

 first makes it practically impossible for the 

 flowers to be fertilised by pollen from their 

 immediate neighbours. 



The devices for wind-fertilisation, however, 

 are on the whole less interesting than those for 

 insect-fertilisation, so I shall devote little more 

 space to describing them. I will only add that 

 two great classes of plants are habitually wind- 

 fertilised : one includes the majority of forest 

 trees ; the other includes the grasses, sedges, 

 and many other common meadow plants. 



The wind-fertilised forest trees belong for the 

 most part to the fivefold group, and have their 

 flowers, as a rule, clustered together into hang- 

 ing and pendulous bunches, which we call cat- 

 kins. It is obvious why trees should have 

 adopted this mode of fertilisation, because they 

 grow high, and it is easy for the wind to move 

 freely through them. For this reason, most 

 catkin-bearing trees flower in early spring, when 

 winds are high, and when the trees are leafless ; 

 because then the foliage doesn't interfere with 

 the proper carnage of the pollen. In summer 

 the leaves would get in the way ; the pollen 

 would fall on them ; and the stigmas would be 

 hidden. Most catkins are long, and easily 



