258 Vines . — Proteolytic Enzymes in Plants . 
It is probable that peroxidase is a modification of oxidase. 
Schonbein observed that if the watery extract of a part of 
a plant giving the oxidase-reaction with guaiacum be allowed 
to stand for some hours, it loses this property, but is still 
capable of oxidizing guaiacum in the presence of H 2 0 2 . The 
converse change has not yet been effected. Moreover, a 
substance or liquid giving the oxidase-reaction also gives the 
peroxidase-reaction. 
With these facts in mind, I took the opportunity of applying 
the guaiacum-test, in one form or other, to all the various 
parts and juices of plants that I employed in the digestion- 
experiments. I found that, with a few exceptions, they all 
gave either the oxidase- or the peroxidase-reaction. My 
results are as follows. 
Oxidase-reaction : given by tissue and watery extract of the 
Mushroom ; extract of Cuscuta shoots ; tissue of the Pear ; 
rind of the Apple, the pulp only when quite ripe ; cortex of 
tuber of Potato ; tuber of Helianthus tuberosus ; root of Dande- 
lion ; feebly by the root of the Carrot ; ripe Grapes (especially 
black) ; watery extract of leaves and stems of the Lettuce. 
Peroxidase-reaction : given by the juice of the Melon, 
Cucumber, and Vegetable Marrow ; the tissue, but not the 
juice, of the Tomato ; the latex of Euphorbia Characias ; the 
milk of the Coco-nut ; extract of Green Peas ; extract and 
root of the Turnip ; the tissue of the bulb of the Onion, 
the Tulip, and the Hyacinth; the rind (but not the pulp 
or the juice) of the Orange; Wheat-germ; the pith of the 
Potato-tuber ; the tissue of the ripe Banana and of the Beet- 
root ; all the non-laticiferous leaves investigated. None of 
these gave the oxidase-reaction. 
It will be seen that my results do not exactly agree with 
those of Bertrand. The divergence is, I believe, due probably 
to seasonal differences in the condition of the parts examined. 
It is at any rate clear that the nature of the reaction given by 
fruits depends upon the degree of ripeness. 
So far as I am aware, there is at present no satisfactory 
explanation of the physiological significance of the presence 
