X] GENERAL OUTLOOK 161 



full eflPect of this cannot be gained unless the spores 

 and seeds be scattered, so that each shall have its 

 individual chance on germination. The plant being 

 immobile cannot effect this of its own motion. 

 External agencies are made available by various 

 adaptive features. It is again the wind, water- 

 currents, and animal agents which are employed in 

 overcoming this disability which follows so directly 

 from the fixed position of plants. Thus we see a strong 

 antithesis between the mobile animal and the immobile 

 plant, which may be traced back ultimately to their 

 differences of nutritive method. It is, however, 

 between the higher terms of the two series that 

 the distinction is most marked. Passing backwards 

 to the simpler, and presumably earlier forms, they 

 assimilate more nearly, till we find ourselves contem- 

 plating forms which occupy a borderland distinctive 

 of neither kingdom, and suggestive of a common 

 origin. 



The spread of germs leads not only to the 

 maintenance of the numbers of the species but also 

 to the occupation of new sites. In fact vegetation, 

 as we see it, may be held to represent a balance 

 struck between the high capacity for increase of 

 the species involved, and the restrictive influence 

 of external circumstances. Examples have been 

 quoted where the former obtains the upper hand, 

 and a rapid spread of a species may be the result. 



B. 11 



