178 Schunck and Brebner . — On the Action of Aniline 
impart a violet colour to the test-papers, but not to the same 
extent in all cases. In some few instances, indeed, the test- 
paper gave a reaction when the leaf or other part of a plant did 
not show any coloration with aniline. In by far the greater 
number of cases, however, where the leaf or other part of a 
plant turns rapidly brown with aniline, its expressed juice 
gives an intense reaction with tetra-paper. The reactions 
indeed seem to run parallel, i. e. when there is an intense 
reaction with aniline we have an intense reaction with tetra- 
paper, while a medium reaction with aniline accompanies a 
medium reaction with tetra-paper, and a feeble or total want of 
coloration with aniline corresponds to a feeble reaction or want 
of reaction with the test-paper. Leaves may from this point of 
view be divided into three classes, viz. (1) such leaves as react 
well with aniline, and the expressed juices of which also react 
well with tetra-paper as well as with acidulated starch iodide 
solution ; (2) such as react with aniline, and the expressed 
juices of which colour tetra-paper but not starch iodide solu- 
tion ; (3) such as do not react either with aniline, tetra-paper, 
or starch iodide solution. The leaves of dandelion and lettuce 
belong to the first class ; their expressed juices affect Schoen- 
bein’s test, but they soon cease to do so as Schoenbein himself 
states. The power to react on tetra-paper is also soon lost, 
but when with this there is also a reaction with starch iodide 
solution it endures for a much longer time. Such differences 
may be due to the fact that these tests differ in sensitiveness, 
the tetra-paper being the most sensitive, the starch iodide 
solution the least so. We made use of another of Wurster’s 
tests for hydrogen peroxide, viz. ^-naphthylamine in con- 
junction with common salt, but without success, since the 
juices of such plants as react well with aniline do not affect 
the reagent named. 
The general conclusion to which our experiments have led us 
is this : — that the cells of many plants, especially of the leaves, 
contain some form of active oxygen in immediate proximity to 
or associated with the protoplasm during the living state of the 
cell. It is necessary to justify this conclusion considering the 
