The Proteases of Plants (II). 
BY 
S. H. VINES, 
Sherardian Professor of Botany in the University of Oxford, 
I N the interval that has elapsed since the publication (April, 1904) of my 
last paper on this subject (1) in this periodical, various facts have 
come to light that contribute not a little to the interest and to the intelli- 
gent apprehension of it : although progress in so large a field has not 
been rapid, for the number of investigators exploring it is still relatively 
small. 
Papain. 
This material has been more fully investigated than any other in the 
vegetable kingdom, and yet it cannot be said to be by any means fully 
understood. The occasion of my reverting to the subject was the reading 
of a paper on it by Emmerling (2), who found that papain digested fibrin 
most actively in a slightly alkaline liquid ; and that, although the amount 
of amido-acids, &c., produced was relatively small, its action was ‘ specifi- 
cally tryptic.’ 
As his results do not altogether agree with those published by me (3), 
I have repeated some of my former experiments and have made some 
under the conditions adopted by Emmerling. His method was somewhat as 
follows: — i,ooo grms. of dry fibrin were covered with feebly alkaline water, 
but the degree of alkalinity is not stated : 20 grms. of Merck’s papain were 
added, as also some toluol. After fourteen days in the incubator at 
37°C., 10 grms. of papain were added; and after fourteen days more, 
further 10 grms. of papai’n. At the close of this prolonged digestion, the 
products were found to be much albumose and peptone, and small quantities 
of arginin, tyrosin, leucin, asparaginic acid, glycocoll, glutaminic acid, alanin, 
and phenyl-alanin. No account is given of any experiments made with 
acid or neutral liquid. 
Apart from the alkaline medium, the conditions of Emmerling’s 
experiments differed from mine in that he used Merck’s preparation of 
papai'n, whereas I used Christy’s preparation ; and further, in that he used 
toluol, and I chiefly HCN, as the antiseptic. Moreover, the relative weight 
of the fibrin to that of the papain was very much larger in his than in mine. 
[Annals of Botany, Vol. XIX. No. LXXIII. January, 1905.] 
