42 FIFTY YEARS OF DARWINISM 



One other consideration brought forward by 

 Mr. Francis Darwin may be briefly discussed. 

 It is well known that plants have the power of 

 adjusting themselves to their individual environ- 

 ment, and that such adjustment may beneficially 

 take the place of a rigid speciahzation. The 

 static condition of plants renders this power espe- 

 cially necessary for them, and the hereditary 

 transmission of the results of its exercise espe- 

 cially dangerous. Where the seed falls, there 

 must the plant grow. The parent was limited to 

 one out of many possible environments; the oif- 

 spring may grow in any of them, and for one 

 that would hit off the precise conditions of the 

 parent and would benefit by inheriting the 

 parental response, numbers would have to live in 

 different surroundings and might be injured by 

 the hereditary bias. 



Mr. Francis Darwin calls attention to the 

 leaves of the beech, which in the interior shaded 

 parts of the tree possess a structure different 

 from that exhibited in the outer parts more freely 

 exposed to Hght. The structure of the shaded 

 leaves resembles that apparently stereotyped in 

 trees permanently adapted to shade, and Mr. 

 Francis Darwin is incUned to regard the fixed 

 condition as a final result of the hereditary trans- 

 mission of the same response through a large 

 nimiber of generations. 



The development of shade foliage in the beech 

 is, I presimie, a manifestation of a power widely 



