ISO ROBERT H. BOWEN. 



tensive work in recent years on plant cytoplasm is undoubtedly 

 that of Guilliermond, who arrives at the conclusion that the 

 fixatives involving osmic acid, so long used by zoologists, give 

 very erratic and misleading results on plant tissue and are 

 therefore in general to be avoided. He himself and his students 

 employ a method which is essentially one of Regaud's formulae, 

 and which in Guilliermond's laboratory seems to have yielded 

 excellent results. I have given this method extensive trial on 

 root-tips with most unhappy results, and have finally discarded 

 it completely as unusable in my hands. The details of the 

 method have never been published very fully, and presumably I 

 have made some unavoidable technical errors which had fatal 

 results. In place of this method I have concentrated on the 

 methods long used by zoologists in the study of animal cytoplasm, 

 and can not agree with Guilliermond's conclusion as to their lack of 

 value for the study of plant cells. On the contrary, I find that 

 with proper experience and controls these methods yield results 

 on plant cells of a value in every way equal to those obtained in 

 animals, and in some respects superior to Guilliermond's method 

 as successfully employed by himself. Quite a number of different 

 methods have been tried, but the following have proved most 

 generally useful: 



Benda using Mottier's ('18) modification of the fixative, 

 and continuing as for the Benda method with animal tissues. 

 This method stains the plastidome more or less specifically in 

 meristem cells, and is very useful for separating it from other 

 components. 



Champy-Kull following the directions exactly as given for 

 animal tissue. This method stains the pseudochondriome (see 

 beyond) more or less specifically and in some cases will separate 

 it completely from all other components of the cytoplasm. 



Kolatchev and Weigl following the directions generally given 

 for animal tissues, but with some slight modifications suggested 

 by experience. These methods were first employed by me for 

 an extensive study of plant cells, the results having been briefly 

 published nearly a year ago (Bowen, '26a). Meanwhile Guillier- 

 mond ('26) had been independently working with the Kolatchev 

 and other osmic methods and his results, published shortly after 



