* 
EMERSON: BLACKENING OF BAPTISIA TINCTORIA 629 
longer retain any soluble matters—as, for example, oxidase. Thus 
after death the direct action of the oxidase on the oxidizable mat- 
ter of the cell sap sets in with a production of colored bodies, as 
is the case in the tobacco leaves. This action can also be noticed 
very well in the juice pressed out from the fresh leaves, since this 
juice, containing cell sap as well as soluble matters previously con- 
tained in the protoplasm, turns brown rapidly on coming into con- 
tact with air. The darkening of the juices of potatoes, beets, and 
other plants depends upon the same principle.” * 
It might be concluded from these two extracts that though 
present in the whole plant of Baptista tinctoria, the enzymes have 
become particularly active in the blackened parts, and that these 
black parts have become susceptible to the enzyme from having 
lost their vitality from some cause. The black leaves do not seem 
dead, and always contain plenty of chlorophyl. Of course the 
blackness is the product of oxidation, but my observations would 
Suggest a possibility that there is a pigment as well, which gives 
the extreme dark color, so much darker than the same product in 
potatoes and beets and tobacco, and so different from the white 
and green of variegated leaves. 
SUMMARY 
The blackening of the leaves of Baptista tinctoria is due to 
oxidizing enzymes. 
There are at least two enzymes, an oxidase which gives an 
opalescent blue with gum guaiac solution and is destroyed by heat 
at about 83°-84° C., and a peroxidase which gives a deep blue 
with hydrogen peroxide and which has a thermal destruction point 
of 86°-87° eH 
Both enzymes can be destroyed with dilute solutions of citric 
acid and sodium hydroxide. 
I wish to express my gratitude to Dr. D. T. MacDougal and 
Dr. W, J. Gies of the New York Botanical Garden, for their kind 
assistance and advice in revising this paper. 
le 3 Loew, Oe Physiological ‘studies of Connecticut leaf tobacco, 40, ve 1900. 
