( 299 ) 
Thus here too a decrease of 30 °/, during the night followed up 
by an equal increase on the following day. If branches on the plant 
are enveloped in black waxed paper the decrease amounts after 
48 hours only to 35 °/,, no great difference with that of 8 hours; 
increase, however, did not take place, so light proves to be a necessary 
factor. The experiments of etiolating told the same. 
If this quantity of salicine disappearing from the leaves was 
removed to the bark, an increase would have to be observed there. 
This was indeed the case, for branches rich in leaves the increase 
of the quantity of salicine of the bark amounted in one night to 
2.5 °/,; for branches with few leaves to 1.1 °/,. 
From the etherextract prepared in the above described manner, 
of the parts of Salix purpurea still another substance could be isolated 
by means of subliming. According to the miero-chemic qualities this 
was a substance resembling phenol and qualified by its compound of 
lead and of lime, besides reaction with tetrachloorchinon as an ortho- 
derivate '). The substance did not show Aldehydreactions. The further 
micro-chemical qualities corresponded to those of the simplest ortho- 
phenol, catechol. After a repeated crystallisation out of benzol the 
melting-point proved to be 104°. Elementary analysis and determina- 
tion of molecular weight confirmed the fact, that it was catechol. 
As the material which furnished the substance was quickly killed 
both in boiling water and in boiling alcohol and the etherextract 
already showed the crystals before sublimation, influence of enzym *) 
is not probable and formation out of resin is not possible. 
Treatment with ferrichloride followed by additon of natrium hydro- 
carbonate also furnished in the tissue the reaction of catechol. The 
red colour was clearly visible in the unopened cells of the sections 
of the bark, young etiolated shoots showed them faintly, older ones 
more. Catechol is like salicine only to be found in the bark *). 
The supposition was aroused that catechol might be the aromatic 
substance, remaining there as definite product of decomposition of the 
salicine. In order to test thé accuracy of this supposition, an investiga- 
tion had to be made whether the quantity of catechol of the parts 
of Salix purpurea were varying. 
For a quantitative determination of the catechol the method of 
1) According to an investigation of Prof. H. Benrens which will shortly appear, 
communicated to me by Miss GRUTTERINK. 
2) The black colour of the dying leaves is caused by the influence of a “tyrosi- 
nase”’ on catechol. 
8) Catechol was also obtained out of Salix Helix L., S. babylonica L., S. vitellina 
L, Populus alba L., P. monilifera Ait, sometimes only very little. 
