The Proteases of Plants (IV). 
BY 
S. H. VINES, F.R.S., 
Sherardian Professor of Botany in the University of Oxford. 
I N the course of the year 1905 an interesting contribution to this subject 
was made by Dean, consisting of two papers (1 and 2 ) on proteo- 
lytic enzymes, the principal results of which may be briefly given as 
follows. 
The objects of the investigations detailed in the first paper, as stated 
by the author, were two : £ in the first place, ... to test a number of different 
plant-tissues in order to confirm, if possible, the results of Vines ; ’ whilst 
‘ the second and more important part of the investigation was to make 
a careful study of the enzymes in some one or two plants.’ 
With regard to the first object, it is somewhat singular that the author 
expresses no opinion as to whether or not he succeeded in confirming my 
results ; but it may be inferred from the account of the experiments that 
he was successful. For instance, in the case of the leaves of the Spinach 
(Spinacia oleracea ), his conclusion is that they £ contain an enzyme capable 
of attacking Witte-peptone, but not acting on the proteids of the tissue, or 
if it does, these proteids do not yield tryptophan on hydrolysis ; ’ a conclusion 
which is, on the whole, in accordance with my earlier observation ( 3 ) that 
these leaves act upon Witte-peptone, but are unable to digest fibrin. 
A similar parallelism exists between his observations and mine on the leaves 
of the Cabbage ( Brassica oleracea). Other experiments, made with material 
that I had not used, the blossoms of the Wild Carrot ( D aliens Car old), the 
leaves of the Chestnut ( Castanea saliva americana), etiolated seedlings of 
a Bean ( Phaseolus Mungo), seedlings of Cucurbita maxima , gave results 
supporting the view, which I have expressed more than once, of the wide- 
spread, if not universal, occurrence of ereptase in the tissues of plants. 
With regard to the second object of Dean’s paper, it was pursued by 
the investigation of the seeds of Phaseolus vulgaris , which seems to include 
the White Haricot Bean and the Scarlet Runner. The result was remarkable. 
It was found that the cotyledons, whether the seeds were ungerminated or 
[Annals of Botany, Vol. XX. No. LXXVIII April, 1906.] 
I 
