( 201 ) 
P. canescens Sm., P. monilifera Ait. and P. tremula L. I found 
here, as in the case of Salix that the young etiolated shoots contain 
no populin and the normal ones a fair amount. In all the species 
investigated, salicin is present and also catechol; for one of these 
plants, P. monilifera Ait. the changes of the two substances during 
the formation of the young shoots were studied. 
In the opening of buds on the tree as well as in etiolated budding 
of branches placed in water, salicin decreases, catechol increases; 
the quantities are in the ratio 100 : 66 and 100:64. The increase 
in catechol is therefore greater than might be expected from the 
decrease in the salicin, and this I think must be ascribed to the 
diminution in the populin (benzoylsalicin). 
I obtained from this Populus, in the manner described above, 
an enzyme, populase, which splits off benzoic acid from populin, 
so that the formation of catechol as end-product of populinhydrolysis 
is indeed very probable 1 ). 
In Populus monilifera and also in P. tremula salicin increases in 
the leaves during the day and decreases during the night, just as in 
the case of Salix ; a quantitative determination of the catechol was 
however impossible on account of the resin present. 
Catalase is present in the young shoots and also catecholase; the 
demonstration of the presence of saligenolase proved difficult as the 
enzyme mixture is not so pure and becomes darker fairly rapidly 
when exposed to air. 
In the species of Populus examined I found considerable quantities 
of saccharose, which there plays the part of a reserve material and 
is present in the leaves, bark and wood (Populus monilifera Ait. and 
P. tremula L.). In the opening of the buds a large portion is used 
and the amount in the bark than falls from 4 % t0 1V# 5 ^ ie 
experiments with bisected leaves also point to a behaviour similar to 
that observed by Brown and Morris 2 ) in Tropaeolum. During the 
night 32% and 35% of the total disappeared from the leaves. Like 
so many other plant organs the young shoots accordingly also contain 
invertin. For further details reference may be made to the publication 
about to appear in the Recueil des Trav. Bot. Neerl. 
Amersfoort , September 1903. 
l ) With the mixture of enzymes from Salix purpurea 1 could not obtain any 
hydrolysis of populin. 
8 ) Brown and Morris. Joura. of the Ghem. Society. 1893. 
