40 
in regard to coloration or for the amount of guaiacum oxidized. 
Tubes having the same depth of coloration must contain equal 
quantities of the enzyms, as all the variables affecting the reaction 
between the enzyms and the guaiacum are fixed. In every case the 
amount of peroxid and guaiacum, the volume of solution, the tem- 
perature, and the time of reaction is the same. If, then, a tube to 
which 2 cubic centimeters of a leaf extract was added gives the same 
coloration as another tube containing 4 cubic centimeters of a second 
leaf extract, it 1s evident that the tubes contain equal quantities of 
enzyms and that the first leaf, therefore, contains twice as much of 
the enzyms as the second. 
There is no exact quantitative method for determining the abso- 
lute amount of these enzyms, but the above method gives the com- 
parative quantities with sufficient accuracy to show significant 
differences. 
Tests were first made, taking samples from different leaves and 
parts of leaves of the same plant, in order to ascertain how great the 
error might be in sampling. It was found that two samples taken 
near together on the same leaf, or from the same relative position 
on leaves of similar age, gave duplicate determinations. Also sam- 
ples from similarly situated leaves on different plants of the same 
age gave duplicate determinations. Samples taken from very old 
leaves differed, however, from very young ones. Also a sample 
taken at the base of a leaf differed slightly from one taken near the 
tip of the same leaf. Therefore, in all the following tests, care was 
used to take the samples from the same relative position on leaves 
of similar age. 
From preliminary tests it was apparent that the quantity of oxi- 
dases in pineapple leaves is very small in comparison with the quan- 
tity of peroxidases! and that the quantity of oxidases varies in the 
same proportion as the peroxidases, hence tests were only made for 
the peroxidases. 
The leaves of the plants grown in the pot experiment described on 
page 21 were tested for peroxidases.? The results are given in the 
following table, in which the first column gives the soil in which the 
plant was grown, the second the condition of the leaves in regard to 
chlorosis, and the third the quantity of peroxidase. The quantity 
of peroxidase in the leaves of the check plant is taken as 10 and the 
other quantities are expressed relative to this. 


1 By oxidases are here meant those enzyms which blue an alcoholic guaiac solution without the addition 
of hydrogen peroxid, and by peroxidases, those enzyms requiring hydrogen peroxid to give the guaiac 
reaction. 
According to Bach and Chodat and Moore and Whitley we may be dealing here with only one enzym, 
peroxidase; the blueing of guaiac solution without hydrogen peroxid being due to a peroxidase plus an 
organic peroxid. 
2 Catalase was also tested for, but found present only in very small and apparently equal quantities in 
the green and chlorotic leaves, 
[Bull. 11] 
