XVI] ANEMOPHILOUS TREES, ETC. 157 



are produced and shed, and that this pollen is remarkably 

 dry, light, smooth, and dusty, while the male flowers 

 are exposed on dangling, tassel-like catkins e.g. Poplars, 

 Oaks, Beeches, &c. or the stamens themselves hang out 

 dangling from the spikelets, as in Grasses, with their large 

 versatile anthers swinging in the wind. 



It occasionally happens that the fields and lanes near 

 pine-forests are so covered with yellow pollen-dust that 

 the appearance of a rain of sulphur is suggested to the 

 people, and even boats at sea have been found dusted 

 with wind -borne pollen. In the case of the Pines and 

 Firs the specific gravity of the pollen is lessened by the 

 peculiar air-balloons developed on opposite sides of each 

 grain, increasing the surface considerably and of course 

 aiding distribution by the wind. 



A further coincidence met with in these anemophi- 

 lous plants is their gregarious habit, so well seen in Pines, 

 Beeches, Grasses, Sedges, &c., and readily interpreted in 

 the light of the foregoing facts. 



All these phenomena, with numerous subordinate ones, 

 such as the large, swaying, feathery plumes of the taller 

 Grasses, the wind-swept habitats of Pines, Firs, Larches 

 and other mountain forest- trees, and so on, are in accord- 

 ance with the adaptation of the flowers to wind-pollination. 

 The following afford examples of wind-pollination 

 (anemophily) : 



Poplars Firs Elms 



Alder Cedars Sweet Gale 



Hornbeam Cypress Sea Buckthorn 



Beech Yew, &c. Pines 



Walnut Birch Larch 



Mulberry Hazel Juniper 



Ash Oaks Arbor Vitse 



Chestnut, 



