ii; 
Vines. — The Proteases of Plants (IV). 
from the reserve proteids. The fact that, In the leguminous seeds, the 
original watery mixture of the cotyledons gave relatively weak tryptophane- 
reaction, which soon became strong under experimental conditions, indicates, 
no doubt, that tryptophane, like the other amido-acids, does not accumulate 
In the cotyledons of the seedling, but is distributed to the growing parts. 
(2) There was present also an enzyme capable of digesting fibrin. It 
may be fairly inferred that an enzyme that can digest fibrin can also digest 
the reserve proteids of the seed. 
I am quite unable to reconcile my results and conclusions with those 
of Dean. Far from being unable to obtain evidence 4 of the presence of an 
enzyme capable of attacking the proteids of the seed/ I have never failed 
to obtain such evidence whenever the seeds were actively germinating and 
the duration of the experiment was sufficiently prolonged. In endeavouring 
to account for the contradiction between us, I am inclined to attribute it, in 
part at any rate, to the relatively short duration of Dean’s experiments : 
this is, I feel sure, the explanation of my own failure to detect autolysis in 
my first experiments with Vicia Faba (see ante, p. 114). But I also 
attribute it, and more particularly, to what seems to me to be a questionable 
proceeding in his method of testing. I notice that, before applying any 
test, whether biuret or tryptophane, the digestive mixtures of Phaseolus 
vulgaris were boiled, then acidified with acetic acid and filtered : in no case 
was the biuret- or the tryptophane-reaction given by a liquid so treated. 
The facts, so far as I know them, are these. A watery extract of seed of 
P. vulgaris gives good biuret-reaction : if the extract be boiled and filtered, 
the filtrate still gives a good reaction, indicating the presence (as I pointed 
out more than twenty-five years ago with regard to seeds generally) of 
a proteose or phytalbumose : if, however, the extract be boiled and also 
acidified with acetic acid and filtered, the reaction is hardly perceptible, 
owing, as I think, to the precipitation of the proteose by the acid. If now 
a small quantity of tryptophane be present in such a solution, it is not 
improbable that It might be carried down wholly or in part by the precipi- 
tates formed by boiling and by acidification. It is highly probable, that had 
the tests been applied to the mixtures in question previously to the treat- 
ment indicated, both the biuret- and the tryptophane-reactions would have 
been obtained. Moreover, I found that some of these leguminous seed- 
extracts did not give the tryptophane-reaction very readily, so that it was 
necessary to add the chlorine-water gradually and to the extent of as much 
as 2-3 vols. before it could be decided whether or not tryptophane were 
present : possibly this detail may have had something to do with the 
observed results. In any case it is obviously desirable to exhaust all 
possible modifications in the methods of such a research, before attempting 
to explain its results by so speculative an hypothesis as that of the direct 
intervention of the protoplasm In the proteolysis of the seed. 
