38 



Mr. J. R. Green. 



[Jan. 14, 



Martin* as being present in Papaw juice. He speaks of it as being 

 precipitated on boiling, the coagulating point being 70 — 74° C. ; pre- 

 cipitated on dialysis ; by C0 2 from dilute solution ; and by saturation 

 of its neutral solution with MgS0 4 . The two appear to be identical. 



An extract of Lactuca sativa was prepared in a similar way to that 

 described in the case of Hanihot. In this there was no globulin, but 

 instead a proteid resembling Vines'sf hemialbumose. It was pre- 

 cipitated on the addition of nitric acid, and the precipitate was largely 

 soluble in excess. Addition of potassic ferrocyanide to this solution 

 gave a precipitate. On filtering off the nitric acid precipitate it was 

 found to be soluble in water and dilute alkalis, and the solution was 

 not coagulated on boiling. The precipitate gave the xanthoproteic 

 reaction. It differed from Vines's body in its solutions not giving 

 the biuret reaction, but agreed with it in not dialysing. After 

 removal of this albumose the extract contained in solution a quantity 

 of the dialysable proteid described as occurring in previous cases. 



Before leaving the investigation it seemed well to examine a plant 

 which should belong to an order not specially laticiferous. The 

 common cabbage (Brassica oleracea, L.), being succulent, was selected. 

 Its examination was not particularly fruitful, bringing to light only 

 the fact that the dialysable proteid was present there as well as in the 

 other plants. It was not in this case examined very closely. No 

 other proteid was found. 



My researches, so far, agree with those of Martin in not showing 

 the presence of true peptone in plants. 



List of Proteids Found. 

 1. Dialysable proteid, resembling peptone. 



This occurred in all plants examined. Its reactions may be sum- 

 marised here : — 



a. Soluble in water. 



b. Not coagulated on boiling. 



c. Precipitated slowly by alcohol, but not coagulated by the 



reagent. 



d. Diffuses readily through membrane. 



e. Is not precipitated by nitric acid, nor by acetic acid and 



by potassic ferrocyanide. 

 /. Is precipitated on saturation of its neutral or acid solution 

 with solid MgS0 4 . 



g. Is precipitated slowly by a stream of C0 2 through its dilute 



solution. 



h. Is converted into true peptone by the action of pepsin. 



i. Does not give the biuret reaction. 



* Loc. cit. 



f Loc. cit. 



