346 BROOKLYN BOTANIC GARDEN MEMOIRS 
We may therefore conclude that the substances necessary for 
oxidation do not suddenly migrate into the nucleus at the moment 
of injury, but that they must exist there before the cell is injured. 
We may ask why the nucleus does not become darkened in the 
normal condition of the cell. The investigations of several workers 
have made it probable that the pigments produced by oxidation under 
normal conditions are at once reduced, giving up their oxygen to other 
substances in the cell. When injury occurs the reduction is checked 
more rapidly than the oxidation, with the result that the pigment 
accumulates. 
It is also possible that injury causes the admission of oxygen to 
the cells. 
In order to test the effect of the indophenol reaction on leaves of 
Monotropa they were torn in two and placed in a mixture of equal 
parts of aqueous I percent paraphenylene diamine and saturated 
aqueous alpha naphthol. “It was found that the result depends some- 
what on the condition of the reagent. In the most favorable cases 
the cells which were torn open became pale purple in color almost 
at once, showing that the reagent readily penetrated them. Usually 
the cell contents (cytoplasm, nucleus and vacuole) became at first 
uniformly tinged with purple. After a while the nuclei would usually 
assume a deeper purple than the remainder of the cell contents. 
The cells lying a little further from the torn surface, which were 
injured but not actually torn open, showed at first a pale yellowish 
color which in some cases became deeper with time and in other 
cases gave way to a purplish tint. In most of these cells the nuclei 
gradually became deeper in color than the other cell contents. Later 
the cytoplasm became in some cases so deep in color as to obscure the 
nuclei. Cells lying still further from the torn surface changed very 
slowly (many remaining unchanged after some hours) so that it was 
evident that the reagent penetrated from the torn surface and not 
through the outer cell walls (which are normally in contact with the 
ain. 
In. most cases the general result, after a few minutes, was a deep 
purple band along the torn edge: inside the purple band was a yellow- 
ish one of irregular outline, followed by nearly colorless intact cells 
further away from the torn edge. 
In I percent aqueous paraphenylene diamine the results were 
similar but the purple color was replaced by a dirty brownish-red 
(with more or less purplish tinge). 
It should be pointed out that these results are most striking with 
4 More rapid penetration from cut or torn surfaces is commonly observed in 
the entrance of reagents into leaves, petals, etc. 
