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The Proteolytic Enzyme of Drosera. 
By JEAN WuirteE, D.Sc., Victorian Government Research Scholar at 
Melbourne University. 
(Communicated by D. H. Scott, F.R.S., December, 1909, and subsequently with- 
drawn. Recommunicated September 6,—Read November 17, 1910.) 
It has been known for many years that if pieces of raw meat be placed on 
the leaves of a living Drosera plant, the meat becomes decomposed, and 
the nutritious parts disappear, having been apparently absorbed by the 
plant. The decomposition was assumed to be brought about by means of 
proteolytic enzymes which were supposed to be present in the excretion of 
the glands with which the foliage leaves are abundantly supplied.* 
As a general rule, some or all of the leaves of a plant growing under 
normal conditions are found to contain insects in various stages of decom- 
position, which have been caught and entrapped by the sensitive glandular 
hairs curling over their bodies and thus imprisoning them. It is found 
that the bodies of these insects undergo the same changes as the bits of 
raw meat did. The hairs do not unclasp the insect’s body until all the 
nutritious matter which it contains has disappeared, and they only release 
their hold when the remaining parts are simply skeleton, wings, ete. 
This decomposition of the body of the insect does not necessarily imply 
that proteolytic enzymes are excreted by the gland cells of the plant, for it 
is quite possible that the solution of the insect’s body, and of the pieces of 
raw meat, may be accomplished by the action of putrefactive, or at least of 
enzyme-producing, bacteria. Tischutkin states that it is solely bacterial 
digestion which occurs in carnivorous plants.t 
The same idea was put forward by Duboisf in his paper “Sur le pretendu 
pouvoir digestif du liquide de l’urne des Nepenthes.” 
The only record I could find of experiments performed for the purpose of 
precipitating the proteolytic enzymes, if actually present, in the glandular 
excretions of Drosera was that of Lawson Tait.§ In 1875 he isolated 
a proteolytic ferment from the glandular secretion of Drosera dichotoma, 
which he states closely resembles pepsin. The method he adopted for the 
preparation of the ferment was as follows:— __ 
“The secretion from the Drosera was collected on a feather, which was 
* “The Soluble Ferments and Fermentation, Reynolds Green, p. 214. 
+ ‘Bot. Centralbl.,’ 1892, vol. 50, p. 304, and 1893, vol. 53, p. 322. 
t ‘Compt. Rend.,’ 1890, vol. 111, p. 315. 
§ ‘Nature,’ 1875, vol. 12, p. 251. 
5 eamaatitey w 
