98 PLANT-LIFE ON LAND [ch. 



chance of survival as a consequence. In the case of 

 the Higher Animals the necessary spread of the race 

 is secured by individual movement, and accordingly 

 they possess no special means for the distribution of 

 their germs. A nest of young birds or rabbits dis- 

 perses of its own initiative on approaching maturity. 

 But in the case of the Higher Plants fixity is a con- 

 dition of nourishment, and such distribution as is 

 necessary must be secured for the germ while young. 

 When once the germ is established as a rooted plant 

 the opportunity is gone for ever. It need then be no 

 surprise, however much the details may command our 

 admiration, that the adaptive arrangements in plants 

 for the distribution of their germs should be varied 

 and eflPective. As in pollination, so also in seed- 

 distribution the foi'ces of nature, wind and water, are 

 used : the former easily wafts away the light seeds of 

 small size, such as those of the Orchidaceae, or 

 Ericaceae, without special adaptive structure. But 

 whole families, such as the Compositae, the Ascle- 

 piadaceae, and the Willows, and especially many trees 

 such as the Sycamore and Elm, show definite mechan- 

 isms which secure distribution of seeds of larger 

 dimensions, by flocculent hairs, or winged expansions, 

 readily caught by the breeze. Water transit is 

 proverbially cheap, and still larger seeds may be 

 conveyed by floating away from the parent plant. 

 This is seen in the Coco-nut, and as an extreme 



