OSTERHOUT: THE NUCLEUS AS A CENTER OF OXIDATION 347 



reagents which have stood long enough to take up oxygen, in conse- 

 quence of which the paraphenylene diamine becomes reddish in color, 

 while the alpha naphthol assumes a dirty grayish-purple. 



When the reagents are freshly made up the action is very slow 

 unless hydrogen peroxide be added. When a mixture is made up of 

 equal parts of each of the reagents previously mentioned and 0.3 

 percent hydrogen peroxide the results are similar to those just de- 

 scribed. But if stronger hydrogen peroxide be used a greater amount 

 of purple coloration is observed in the cells. 



When 3 percent hydrogen peroxide is used (in place of 0.3 percent) 

 the following changes may be observed. A pronounced purple color 

 appears at once in the torn cells : this spreads rapidly to the adjacent 

 cells, which are still intact, and may extend through several rows of 

 intact cells. In these intact cells the first appearance of change is the 

 formation of purple granules of indophenol in the vacuole. The vacu- 

 ole becomes filled with these granules which show active Brownian 

 movement. Occasionally some of them come in contact with the 

 nucleus (or the film of cytoplasm which covers the nucleus) and stick 

 fast to it. At this time nucleus and cytoplasm are usually free from 

 granules or coloration. The purple color grows more intense until 

 the details of cell structure become obscured. 



The general conclusion is that while the indophenol reaction indi- 

 cates that the nucleus is the center of oxidation it does not give as 

 definite information on this point as the formation of natural pigments 

 within the cell as the result of the oxidation of substances normally 

 present. 



Summary 



Injury produces in the leaf-cells of the Indian Pipe {Monotropa 

 uniflora), a darkening which is due to oxidation. The oxidation is 

 much more rapid in the nucleus than in the cytoplasm and the facts 

 indicate that this is also the case with the oxidation of the uninjured 

 cell. 



