Notes . 
411 
then decolourised, and the presence of sugar and its amount in each 
was volumetrically determined by means of carefully prepared Fehling’s 
solution : 
Jar No. Nature of Mixture. Amt. of Sugar ( estd . as Dextrose'). 
per 100 ce. 
1 — 50 cc. extract + 50 cc. starch-solution . . . -0793 grme. 
2— 50 cc. extract ( boiled ) + „ ... .0450 „ 
3— 50 cc. extract + 50 cc. „ + thymol . . -0740 „ 
4 — „ „ + „ „ + boracic acid -5 grme. -0690 „ 
5 - it „ + » distilled water . . . .0444 „ 
6 — ,, starch-solution + ,, „ ,, . .. no trace. 
The starch-solution used was obtained by boiling *5 grme. of 
starch with 100 cc. of dist. water; the liquid was allowed to cool 
and settle in a closed vessel, and only the nearly clear supernatant por- 
tion was used. 
The activity of the ferment is represented by the difference between 
the amount of sugar in the leaf-extract to begin with, and the amount 
ultimately found in the mixture of leaf-extract and starch-solution : thus, 
from Nos. 2 and 5 it appears that the amount of sugar originally in 
the extract was about -045 per cent., so that the amount of sugar 
formed from the starch-solution by the ferment in No. 1 is about *034 
per cent. It may be objected that this represents a very small amount 
of diastatic activity, so small indeed that it may be neglected as a 
factor in the almost wholesale conversion of starch into sugar which 
takes place in the living leaf ; but this objection is deprived of weight 
by the consideration that, though the amount of ferment which can be 
extracted from leaves at any given moment is so small, yet the ferment 
is doubtless being constantly secreted, so that the total amount secreted 
during a night, for instance, would suffice to effect the observed con- 
version of starch into sugar. 
In two cases ( Rheum hybridum , Daucus Caro/a) somewhat peculiar 
results were obtained. In the former, the mixture of leaf-extract and 
starch-solution was found to contain less sugar (-1587°/^) than the 
mixture of leaf-extract and distilled water (-2 7o2°/ 0 ), after standing 
for 24 hours: in the latter also the mixture contained less sugar 
- (-io 527 o ) than the leaf-extract diluted to the same bulk (*1250°/^). It 
would appear that, in these cases, the added starch was not attacked 
at all : hence the question arises as to the explanation of these varying 
amounts of sugar. An explanation is suggested by the further 
observation, made as a control-experiment in the case of Daucus , that 
