4io 
Notes . 
and of Brasse 1 , which seem to prove the presence of diastase, Wort- 
mann finds that watery extracts of green leaves have no diastatic action, 
and concludes that the normal conversion of starch into sugar is 
effected in the living leaf by the direct action of the protoplasm. 
I am unable, within the limits of a note, to criticise Wortmann’s 
experiments in detail, or to give a full account of my own. In the 
way of criticism I would only point out that Wortmann’s method is 
open to serious objection : the mixing of a certain quantity of leaf- 
extract with a certain quantity of starch-solution, and then using the 
iodine-reaction as a means of determining the amount of chemical 
change effected, is not a method calculated to give definite results; 
for, as Wortmann himself admits, the colouring-matters and other 
foreign substances in the leaf-extract interfere with the colour-reactions 
with iodine. Again, it is disadvantageous to filter, as Wortmann did, 
the watery extract of the leaves before adding it to the starch-solution. 
I have found that the turbid extract, merely strained, is much 
more active than the clear extract obtained by filtration : probably 
Wortmann’s negative results were mainly due to this cause. 
There is one experiment upon which Wortmann lays so much stress 
that it calls for special notice. He finds that the starch will not 
disappear from the cells of a living leaf if the leaf be kept in an 
atmosphere of carbon dioxide; and from this he concludes that the 
transformation of starch into sugar must be a direct vital act of the 
protoplasm, dependent upon the supply of free oxygen. Assuming 
the correctness of the observation, a more simple and satisfactory 
explanation of it would be that, in the absence of free oxygen, the 
protoplasm is unable to secrete the necessary diastatic ferment. 
My experiments appear to establish the fact that a diastatic ferment 
is present in green leaves. The following description of a single 
typical experiment will give an idea of the methods adopted and of 
the nature of the re suits obtained : 
500 grmes. of grass (with some Clover and Achillea intermixed), cut 
from a lawn, were well triturated in a mortar with 500 cc. distilled 
water : the mass was pressed through a strainer and a turbid slightly 
acid liquid, the leaf-extract, was obtained. In the afternoon, about 
four hours later (4.30 p.m.), the following mixtures were made in six 
jars, and were allowed to stand on the laboratory table till 6.45 a. m. 
the following morning, when they were all boiled at once ; they were 
1 Comptes renclus, t. xcix, 1884. 
