478 UNTOWARD INFLUENCES. 



white spots intermingled with the green of the leaf, corne from 

 eastern Asia, notably from Japan. 1 



1249. The lease of life of any given plant is fixed primarily 

 by the inherited character : 2 hence we have annuals, biennials, 

 and perennials ; but these differences are not in all cases abso- 

 lute, in some they are even ill-defined. The lease of life is 

 modified secondarily by external influences, which have been 

 sufficiently discussed in the present volume. In conclusion, 

 attention should be called again to the fact (see Chapter V.) 

 that in man}- instances the duration of the life of the plant is 

 determined largely by mechanical factors, especially the strength 

 of materials. 



1 Morren : Here"dite de la Panachure, 1865, p. 7 ; Frank : Pflanzenkrank- 

 heiten, p. 465. 



a The student should examine Minot on "Life and Growth," 



