Vines. — Proteolytic Enzymes in Plants. 257 
These facts are insufficient to suggest any general explana- 
tion of the conditions of the formation of tryptophane in the 
plant-body. In the case of fruits, its presence is certainly 
associated with the process of ripening ; in the case of 
seedlings, with the presence of a supply of reserve proteid. 
Inasmuch as tryptophane is a product of catabolism, the 
detection of it in the tissues may serve as a means of deter- 
mining the exact seat of these processes and the conditions 
under which they take place. 
Oxidase and Enzyme. 
If tincture of guaiacum be treated with an oxidizing agent, 
such as chlorine-water or potassium permanganate (KMn0 4 ), 
it is oxidized and assumes a deep blue colour. It was 
ascertained by Schonbein (5) and others that various vege- 
table substances, for instance, roots, stems, leaves, and flowers 
of the Dandelion (Leontodon Taraxacuiri), the rind of the 
potato, &c. similarly effect the oxidation of guaiacum at the 
expense of the oxygen of the air. More recently, Bertrand 
(6) has found that the reaction is induced by many parts of 
plants — the roots of the Beet, the Carrot, the Turnip, and the 
Dahlia ; the shoots of the Asparagus ; the rhizome of Canna ; 
the stems and leaves of Lucerne, Clover, and Rye-Grass ; the 
leaves of the Jerusalem Artichoke (Helianthus tuber o sits'), and 
of the Beet ; the fruits of the Apple, the Pear, and the 
Quince ; the petals of Gardenia ; the latex of species of 
Rhus ; and he has also ascertained that the reaction is due to 
the presence of an extractable organic substance that may be 
generally termed oxidase. 
Schonbein further observed that portions of plants that 
cannot induce the direct oxidation of guaiacum can do so 
indirectly, if a small quantity of hydrogen peroxide (H 2 0 2 ) 
be present, the oxidation being effected by the oxygen set 
free on the decomposition of the H 2 0 2 . This property, 
indicative of a lower degree of oxidative activity, is very 
commonly possessed by plants, and attaches to a substance 
distinguished as peroxidase. 
s 
