Vines. — The Proteolytic Enzyme of Nepenthes. 567 
fortunately I am unable to refer to his original paper as it 
is written in Russian, and have therefore to fall back upon 
the abstract given in the Botanisches Centralblatt. He denies 
the secretion of a peptic ferment by any ‘ insectivorous ’ plant, 
supporting his contention by experiments with various plants 
of this class, including Nepenthes , on which he made the 
following observations, which I quote from the abstract: — 
c Openings were made in the lateral walls of unopened pitchers, 
which therefore could contain no Bacteria, and liquid Was 
drawn off by means of a pipette and placed in test-tubes 
which contained water (neutral in some, acid in others) and 
cubes of white of egg, the operation being performed through- 
out under antiseptic conditions. The result was negative ; 
after forty-eight hours at a temperature of 37*5° C., the cubes 
were unaltered : hence the pitcher-liquid contains no peptic 
enzyme. In order to anticipate the objection that the pitchers 
used may have been too young, the experiment was repeated 
in a modified form. Sterilized cubes of white of egg were intro- 
duced into closed pitchers through openings made in their 
walls, the openings being immediately closed up, and the 
plants left to themselves. When the pitchers opened them- 
selves four days later, the cubes of white of egg were found 
to be unaltered ; the liquid had a strong acid reaction, but 
it contained no peptone, and but very few Bacteria were 
present. The liquid from these pitchers was then placed in 
test-tubes with fresh cubes of white of egg ; the cubes under- 
went solution in four or five days, that is, after a time which 
permitted the Bacteria to multiply to a very considerable 
extent.’ 
The conclusions of Dubois and of Tischutkin have been 
adversely criticized by Goebel 1 , who adduces evidence 
favouring the view of the presence of a proteolytic enzyme in 
the secretion of Nepenthes. For instance, he made the following 
observations on three pitchers of N. paradisiaca of different 
ages. The oldest pitcher contained a small quantity of 
1 Pflanzenbiologische Schilderungen, IT, 1893, p. 186. 
