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short shoots, containing too small a quantity of HCN, and the diffe- 
rence between the two portions compared lay within the range of 
individual variation. If on the other side one will use larger branches, 
it is exceedingly difficult to choose two portions which can be compared; 
the limits of error of the experiment presently widen, and consequently 
the desired end is not reached. The experiments on branches longitudi- 
rally cut in two, which were undertaken with P. Laurocerasus, one 
moiety being immediately analysed, the other one, bearing the buds, 
being put in the dark till it had given off etiolated shoots, failed for 
the same reason. In consequence this question must remain unan- 
swered for the present; perhaps experiments to be made next spring 
with rooted cuttings will meet with more success. 
1 will now endeavour to show that the cherry-laurel behaves in 
so far quite like P. Padus, that the parts situated immediately below 
the growing shoots retain their percentage of HCN nearly completely 
unchanged. Here the experiment becomes in a certain degree com- 
plicated, but also on the other hand is made more interesting, by the 
presence of the leaves. Therefore L must begin to tell something 
respecting the amount of HCN in these organs. 
They have been analysed several times for pharmaceutical purposes. 
I only will recall here that FrücxKiGer *) gave as the average of esti- 
mations, protacted during ten years, on cherry-laurels growing 
on the banks of the lake of Thune, 0,12°/, of the weight of 
fresh leaves. Folia Laurocerasi, bought in December and January 
from GROENEVELD and Linpnout, yielded O,14—0,16°/,, while the 
shrubs grown in the Botanical Garden at Amsterdam were found to 
contain in their leaves an amount ranging from 0,12 till 0,21°/,, 
0°? 
according to the individual analysed. Those were at least the quantities 
found in the course of the season December—May. The last named 
high figure is regularly yielded by the leaves of a certain shrub, 
that consequently could if wished be made the starting point of a 
selection to obtain a race containing much prussic acid. 
It also may be of importance to acquire an idea of the absolute 
quantity of hydroeyanie acid contained in one leaf. Of course, owing 
to the variable dimensions of these organs, this quantity also varies 
considerably. L found 0,0015 — 0,0036 gr. HON, the maximum-value 
in large leaves supplied by GROENEVELD and Laxpnoer, with a per- 
centage of 0,15°/,. , 
Before studying the modifications in the amount of HCN in the 
1) Pharmakognosie des Pflanzerreichs. de Aufl. 1891 p. 766. 
