( 579 ) 
separately in a small bottle with the solution of the stain, the neck 
of the bottle being closed with a plug of cotton wool to prevent 
evaporation. 
After the experiment the twigs were examined at ditferent levels 
by microscopic sections. Transverse, radial and tangential sections 
were examined in oil of cloves , a medium in which Saureviolett is 
insoluble, so that the stain remained properly localized. The sections 
were cut without the use of any liquid and were at once placed in 
the oil of cloves. The slight water content of these preparations did 
not interfere. After a very short time the oil had thoroughly permeated. 
This method had moreover the advantage, that after most of the 
clove-oil had been wiped away, the preparations could be very well 
enclosed in Canada balsam, without further treatment. 
A comparison of the behaviour of the xylem elements of living 
and dead branches brought out the following differences: 
living branch I dead branch 
a. torus of the closing membrane of a. torus not stained, or only very 
the bordered pits deeply stained. slightly. 
b. adjoining the lumen, a thin b. the walls of the vessels, fibres 
layer of the wall in the border ' and parenchymatous cells are 
of the pits is stained. The walls ! stained uniformly. 
of vessels and fibres are only i 
stained in a very thin layer, I 
which is immediately adjacent j 
to the lumen. 
c. contents and wall of the cells I c. contents of the cells are coloured, 
of medullary rays and wood 
parenchyma are unstained. 
The deep staining of the tori in living branches was especially 
noticeable, also in transverse sections, the more so because the 
staining of the layer next to the lumen in the walls of vessels and 
fibres was often difficult to see and because the living cells of the 
medullary rays and parenchyma were quite colourless. 
In the wood of Salix and of Fagus, in which the tori cannot 
otherwise be seen at all, they were made very obvious by this 
staining of living branches. 
The staining of the tori by eosine in a living branch of Ginkgo 
was already mentioned by Janse in “Die Mitwirkung der Markstrahlen 
bei der Wasserbewegung im Holze” (Jahrb. f. Wiss. Bot. 1887 
Ikl- XVIII), In this case also the stain had ascended the branch: 
39 
Proceedings Royal Acad. Amsterdam. Vol. XII. 
