Chap. IV] THE AIR 79 



2. Wind and Reproduction. 



The flora of open windy tracts of land shows the influence of air- 

 currents no less in its reproductive than in its vegetative functions. Ancnw- 

 pJiily in pollination is much more frequent in exposed localities, where 

 the air is usually in motion, than in the calm interior of forests. The main 

 mass, even if not the majority of species, of the vegetation of grassland 

 and swamps is composed of anemophilous plants, such as grasses, sedges, 

 rushes, species of Plantago, Sanguisorba, Thalictrum, and the like. Lofty 

 trees such as the Coniferae and most Amentaceae are in many cases 

 dependent on wind-pollination. On the other hand, the shrubs and herbs 

 of the forest are chiefly entomophilous. The connexion between the wind 

 and anemophily is most clearly seen in the coast-islands of the North Sea. 

 Thus in Spiekeroog J. Behrens found one-third of the species that 

 blossomed in May had anemophilous devices. Such plants were especially 

 found near the fiats, where the winds blow strongly, whilst the entomo- 

 philous species, as well as their pollinators, occupied the sheltered spots. 

 In Chapter V (Animals) the connexion between insular stations and 

 method of pollination will be more fully discussed. 



Still more evident than in the case of pollination is the connexion 

 between the means of dissemination and the amount of wind prevailing in 

 a locality. Anemophilous adaptations in the seeds, or in the fruits that 

 contain them, such as diminutive size, low specific gravity, wings or hairs, 

 are chiefly to be found in wide level grassland (steppe, savannah), in 

 desert, in open swamp, and in the open parts of high mountains. As 

 a rule, it is useless to look for berries in such places. Adaptations 

 facilitating the transport of seeds by animals are, however, not wanting ; 

 they are not correlated with birds that eat berries, but with grazing 

 quadrupeds and with carnivorous swamp-birds to whose bodies the seeds 

 become attached. On the other hand, among the shrubs and herbs of the 

 forest or scrub, berries and other adaptations to the animal life of the 

 forest form a common feature. Tall trees and lianes, again, are often 

 provided with anemophilous means of dispersal, and so indeed are many of 

 the epiphytes that grow in the interior of forests. The seeds or spores 

 of the latter are, indeed, so small and light that the weak vertical currents 

 of wind that prevail in forests are sufficient to carry them to their destina- 

 tion among the stem and branches, until owing to their stickiness they 

 adhere to the bark or become caught in its cracks. 



The sea-coasts form an exception to the rule that anemophilous means 

 of seed-dispersal predominate in very windy places. The sea is the vehicle 

 for the seeds of most littoral halophytes. Species of plants whose seeds are 

 easily conveyed by the wind, but which sink in sea-water, would with 

 difficulty hold their own on the sea-shore, as their seeds would be either 



