PLANT STRUCTURE • 15 



involving carbon dioxide in photosynthesis may therefore 

 be associated v^ith the cytoplasm, and this w^ould involve 

 diffusion of intermediates as one step in the over-all 

 mechanism. 



Chloroplasts do not arise de novo but are independent 

 self-reproducing entities, inherited generally from the cyto- 

 plasm of the female cell. Thus Ternetz found with a species 

 of Euglena that it w^ould give rise to cells v^ithout chloro- 

 plasts or leucoplasts when grown in the dark; these cells 

 when grown separately never formed chloroplasts again. 

 The development of the chloroplast is determined by Men- 

 delian factors and by factors depending on the functional 

 and physiological differentiation of the tissues. For example, 

 in maize numerous independent genes have been identified 

 which determine albinism and influence the pigmentation 

 of the chloroplasts. 



