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. 
