MORPHOLOGY OF ANGIOSPERMS. 



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of irritability. Movements of organs are of two general classes : 

 (i) Those due to stimuli which originate in the plant and (2) 



Fig. 75. Branch of Tansy (Tanacetum vulgare) showing closely alternating, deeply 

 pinnatifid or pinnately-divided leaves, the divisions being linear, oblong and variousl>- 

 lobed and incised. 



those due to the influence of external factors. To the former class 

 belong all those movements which occur during the course of 



