28 q 
Notes . 
The results we have obtained in following up this inquiry are, we 
think, of considerable interest. 
If the diastase is determined in a certain number of half-leaves 
taken during the day, and the other halves of these leaves are left still 
attached to the plant and are examined some hours after darkness has 
set in, we find that in the latter case, under conditions in which the 
leaf is being depleted of starch, the diastase increases very much in 
amount. 
We give here the observed increases in diastase in the leaves of 
Tropaeolum under these conditions. 
At io p.m. on an autumn evening there was 35*6 per cent, more 
diastase than there was at 5 o’clock in the afternoon. 
In another case at n o’clock at night there was 70-3 per cent, 
more diastase in the leaf than at 3 o’.clock in the afternoon. 
In a third case at 5.30 in the morning there was 63-5 per cent, 
more diastase in the leaf than at 4 o’clock in the afternoon previous. 
We find that the same increase in diastase takes place if the leaves 
are plucked and placed in darkness with their stalks in water. In 
leaves of Tropaeolum , so treated for eighteen hours, the diastase more 
than doubled in amount, whilst the starch had almost entirely 
disappeared. 
No matter how the experiments were conducted, we were always 
led to the same result, — the conditions which are favourable for a 
decrease in the leaf-starch result in an increase of the leaf-diastase. 
At first sight it seemed possible to explain this accumulation of 
diastase in darkness without having to fall back upon the supposition 
that the rate of production of the diastase by the living elements of 
the cell is variable. It is quite possible to imagine that the protoplasm 
of the assimilating cells secretes a certain definite amount of diastase 
which is constant under all conditions of insolation. As long as 
assimilation is proceeding with sufficient activity to maintain an excess 
of starch in the chloroplasts or amyloplasts this diastase is being used 
up in re-dissolving the starch, and consequently the enzyme does not 
accumulate in the cell. Supposing however that the plant is now 
placed in the dark, the starch diminishes and finally disappears, and 
there is consequently a diminished draft upon the diastase which now 
accumulates in the cell, not because the enzyme is being produced 
faster, but because less is being used up in a given time for 
hydrolysis. 
