622 EMERSON: BLACKENING OF BAPTISIA TINCTORIA 
has classified them into three large groups according to the effects 
which they produce : 
A. Soluble hydrating ferments or enzymes. 
B. Soluble oxidizing enzymes. 
C. Enzymes causing molecular decomposition. 
It is with the middle group that this paper is concerned. The 
oxidizing enzymes are found in both animals and plants, are widely 
distributed in all the parts of plants and in every kind of plant 
from bacteria to the phanerogams. Laccase, the first of the oxi- 
dases to be discovered (in 1883 by Yoshida, a Japanese chemist), 
makes lacquer; malase acts on fruits and causes apples and pears 
to turn brown when exposed to air; and others are connected 
with the ripening of olives or are found in wine. Without giving 
them actual names, like the foregoing, there are two kinds of OXI- 
dases generally recognized by the differences of their reactions, 
one “oxidase,” which oxidizes guaiaconic acid (the characteristic 
reactive in the guaiac resin) to guaiac blue without the aid of 
peroxide of hydrogen, and the other ‘“ peroxidase,’ which oxidizes 
it only when this substance is present.* 
There is a third, catalase, which according to Loew 7 is of 
general occurrence in the vegetable kingdom. 
In this paper only very general experiments are described, but 
the methods of preparation of the material and ways of applying , 
the tests are the ones usually adopted for this kind of work. 
Preparation of material. — Fresh stems were gathered and the 
leaves stripped off; flowers also were used when present, but not 
the pod or thicker stems, as these could not easily be sufficiently 
broken up. The leaves were ground up in a mortar with quite 
fine sand, which had been previously treated with dilute hydro- 
chloric acid and washed until no acid reaction could be detected 
with litmus paper, then dried in the sun. When ground, the 
leaves were covered with distilled water and left to macerate for a 
period of a half to one hour; the extract was next filtered, the 
leaves being squeezed in a cloth as dry as possible and thrown 
away. The filtrate was treated with three times its bulk of strong 
EE eee eae eS Do rege 
* Loew, O. — and Selene of cigar leaf eitinecs, a7; wn S. Dept 
Agriculture ee 0. 59.) 
+ Loew, O. Ciiatae: pe **. S. Dept. Agriculture Rep. No. 68.) 1901. 
