THE WIND AS CARRIER. 143 



the regular types with which we are familiar; 

 yet intermediate cases help to bridge over the 

 gap for us. 



For example, in the alder we get a type which 

 seems to stand half-way between the nettle and 

 the hazel (so far, I mean, as the arrangement of 

 the flower is concerned, for otherwise the nettle 

 belongs to a quite different family). The male 

 and female catkins of the alder grow on the 

 same tree ; the males consist of numerous 

 clustered flowers, three together under a scale, 

 which nevertheless, when we take the trouble to 

 pick them out and examine them with a pocket- 

 lens, are seen to resemble very closely the male 

 flowers of the nettle. Each consists of a four- 

 lobed calyx, with four stamens opposite the 

 sepals. The female flowers have degenerated 

 still further, and consist of little more than a 

 scale and an ovary. 



Other well-known wind-fertilised, catkin-bear- 

 ing trees are the oak, the beech, the birch, and 

 the hornbeam. But the willows, though they 

 bear catkins, and were once no doubt wind- 

 fertilised, have now returned once more to 

 insect-fertilisation, as you can easily convince 

 yourself if you stand under a willow tree in 

 early spring, when you will hear all the branches 

 alive with the buzzing of bees, both wild and 

 domestic. Nevertheless, the willow, having 

 once lost its petals, has been unable to develop 

 them again. Still, its catkins are far hand- 

 somer and more conspicuous than those of its 

 wind-fertilised cousins, owing to the pretty 

 white scales of the female bunches, and the 



