300 



LECTURE XIV. 



FIG. 36 (after Stahl). Sections of the phylloid stem of Lemna trisulca. 



A. Position of the chlorophyll-corpuscles when the stem is exposed to intense 

 light (light-apostrophe). 



B. Position of the corpuscles in diffused daylight (epistrophe). 



C. Position of the corpuscles in darkness (dark-apostrophe). 



We come, then, to the same conclusions in the case of 

 movement as in the case of growth. Movement is dependent 

 upon an evolution of energy, that is, upon destructive meta- 

 bolism, but it is nevertheless a distinct process capable of 

 being affected by conditions which do not affect destructive 

 metabolism. 



We will now go on to study the nature and causes of 

 the movements rather more closely. Most of the move- 



