260 Vines.- — Proteolytic Enzymes in Plants. 
these plants also. The marked proteolytic activity of the 
Cucurbitaceae, of which I have given several instances, taken 
in connexion with the great development of the sieve- 
tissue in plants of this Order, suggests that the proteases 
are specially located in this tissue. This being so, there 
would seem to be a definite relation between the oxidative 
and the digestive properties of the contents of the laticiferous 
and sieve tissues. 
Concluding Remarks. 
The experiments previously described suffice to prove that 
the juices or the tissues of various parts of the most widely 
different plants so act on certain proteids, whether contained 
in them or added to them, as to give rise to a substance 
giving a reaction similar to that of tryptophane with chlorine- 
water. 
It has been tacitly assumed throughout that the substance 
in question is actually tryptophane: but inasmuch as the 
conclusions to be drawn entirely depend upon it, it is neces- 
sary that the assumption should be justified. I have not, 
I admit, isolated the substance, and so placed the matter 
beyond doubt ; that is a task that could only be successfully 
undertaken by a professed physiological chemist ; but I am 
able to adduce other convincing evidence. It is known that if 
a liquid, which has given the tryptophane-reaction, be shaken 
up with some amyl alcohol, the pink chlorine-compound 
dissolves in the alcohol which separates out as a supernatant 
layer coloured pink. If this coloured solution be examined 
spectroscopically, the spectrum is found to present a well- 
marked absorption-band in the green, on the yellow side of 
the Thallium-line (571-540 /qx). I have applied this test 
with success to several of the digestion-liquids, and have in 
all cases found that the chlorine-compound dissolves in amyl 
alcohol, and that the pink solution gives the absorption-band 
characteristic of the chlorine-compound of undoubted trypto- 
phane. I conclude, therefore, that the substance which gave 
