No. 449.] STUDIES ON THE PLANT CELL. 381 



higher members of the Phaeophyceae and Rhodophyceae and in 

 the Siphonales, Charales, Cladophoraceae and some smaller 

 groups of the Chlorophyceae. The Conjugales whose chromato- 

 phores are especially elaborate have cells essentially solitary in 

 their life habits and with a very remarkable adjustment of the 

 cell organs to one another to give almost perfect symmetry. 

 With the splitting up of the chromatophore came the loss of the 

 pyrenoid and the final result was the compact plastid so charac- 

 teristic of plants above the thallophytes. 



I 



(c) Cytoplasm. 



There is no region of the plant cell that maintains such varied 

 relations to its environment and performs so many visible 

 activities as the cytoplasm. For this reason the accounts of its 

 structure and behavior have been diverse and there has developed 

 a nomenclature of its parts that is confusing and somewhat 

 difficult to harmonize. 



Strasburger has for many years (since 1892) employed the 

 term kinoplasm to distinguish an active portion of the cytoplasm 

 (concerned with the formation of spindle fibers and other 

 fibrillae, centrospheres, centrosomes, cilia, plasma membranes, 

 etc.) from more passive nutritive regions which he called tropho- 

 plasm. Kinoplasm corresponds closely to the archoplasm of 

 the animal cell (Boveri, 1888). This classification has been 

 criticised especially by Pfeffer ( : oo) on the ground that it 

 employed names signifying physiological differences when the 

 distinctions as far as we know are those of morphology alone. 

 However the physiological behavior of kinoplasm and tropho- 

 plasm becomes very real to anyone who studies extensively cell 

 activities and the morphological characters serve to emphasize 

 these peculiarities. The truth seems to be that cell studies 

 cannot be pursued from the standpoint of physiology or mor- 

 phology alone but must combine these attitudes. And in the 

 union it is hardly possible or perhaps desirable to construct 

 a terminology with strict regard to either field of study. We 

 shall use the terms kinoplasm and trophoplasm grouping the 

 various cytoplasmic structures under these heads. 



