Vines. — Proteolytic Enzymes in Plants (//). 6 1 1 
study of inulin, though the discovery of the enzyme 
innlase was made by Green (1887) i n the tubers of the 
Jerusalem Artichoke (. Heliantlms tuber osns). But the fact 
of more immediate interest in connexion with the subject 
of the present paper is that Leitgeb ( 7 ) found the roots, in 
a state of rest, to contain considerable quantities of asparagin 
and tyrosin as nitrogenous reserve-material. On this ground 
the Dahlia-roots seemed likely to be promising material for 
digestion-experiments, which I have accordingly made, 
together with some incidental observations on the presence 
of tyrosin. 
The expressed juice of the tuberous roots immediately 
assumes a dark colour owing to the action of the oxidase 
which Bertrand (8) found to be present, and which he termed 
tyrosinase , upon the tyrosin in solution. On filtration, a brown, 
opalescent, distinctly acid liquid is obtained, which gives 
strong xanthoproteic reaction, strong Hofmanns reaction 
with Millon’s reagent, and oxidase-reaction with guaiacum, 
but no biuret-reaction : it gives a tryptophane-reaction which 
is not easy to perceive on account of the brown colour of the 
liquid. On boiling the juice there is a considerable precipitate : 
the clear filtrate gives the same Hofmann’s and xanthoproteic 
reactions as the unboiled liquid. 
These reactions, especially the Hofmann’s reaction with 
Millon’s reagent, in which a brilliant pink colouration appears 
on heating, followed by the formation of a similarly coloured 
precipitate, indicate the presence of tyrosin in considerable 
quantity. More definite evidence is afforded by the applica- 
tion of Morner’s ( 9 ) test. As this reagent is not yet well 
known, I give its preparation. It is a mixture of 1 vol. of 
formalin (40%) with 45 vols. of distilled water, and 55 of 
concentrated sulphuric acid. Heated with tyrosin, a striking 
green colour is produced. I found that on adding some of 
this reagent to Dahlia-juice, the green colour was developed 
without heating ; the effect of heating was to give rise to 
a brown colour, due probably to the action of the H 2 S 0 4 on 
the inulin present. 
T t 
