382 PHOTOSYNTHESIS 



described. It is apparent that considerable differences in the surface 

 exposed to the Hght may result according as to whether the flat side or 

 the profile of the chloroplast is in the direct line of the incident rays. 

 The same result is attained in some plants through the chloroplasts in 

 each cell forming one or more congregate masses under conditions of 

 intense illumination. Through mutual shading the total surface exposed 

 to illumination is reduced. All these alterations in the position of the 

 chloroplasts may also be brought about by changes in external condi- 

 tions other than light. Mechanical injury, removal of water and changes 

 in temperature induce the same alterations. However, no accurate de- 

 terminations have been made of the influence on the rate of photosyn- 

 thesis of these alterations in the position of the chloroplasts.®^ 



''Frank, Jahrb. zviss. Bot., 8, 216 (1872). Stahl, Bot. Zcitq.. 38. 297, 321, 345, 

 361,_ 2,77, 393, 409, 868 (1880). Haberlandt, Jahrb. unss. Bot, 13, 74 (1882). 

 Schimper, ibid., 16, 1 (1885). Senn, "Die Gestalts- und Lageveranderung der 

 Pflanzenchromatophoren," Leipzig (1908). Liese, Beitr. allg. Bot., 2, 323 (1922). 



