270 
BRYCE : 
with tincture of alcannin, and reddish orange with Sudan 
glycerine, and the characteristic, contorted appearance of a 
strand of rubber is plainly evident. Digestion of sections in 
Schulze’s maceration mixture for 30 minutes in the cold leaves 
the rubber content intact, while other cell contents are dis- 
solved. Sections of nodules freshly taken from a tree show 
that the latex vessel content is already coagulated ; no latex 
oozes out from the cut surface of the central core. 
Tannin cells surround the latex vessels of the core in a layer 
of varying depth. Some cells contain a yellowish tannin, 
which readily turns blue with ferrous sulphate solution, and 
appears not to differ from tannin in normal cortex. Similarly, 
just as in normal cortex, cells with a dark brown tannin content 
are present. A few of these readily turn blue with ferrous 
sulphate, but the majority are acted on only very slowly, and 
apparently contain an insoluble tannin or tannin compound, 
which is highly resistant even to Schulze’s maceration mixture. 
In the core the cell walls of the latex vessels, the latex 
vessel content, and the cell walls of the tannin cells and of the 
neighbouring cortical cells are all of a yellow colour. This 
colouration appears to be due to the infiltration of some 
coloured substance. In some places only the middle lamella 
is coloured, and occasionally the colouring matter is found 
occupying neighbouring intercellular spaces. Again, only the 
secondary thickening layers of a cell wall may be coloured. 
Generally, however, the whole wall is coloured. The colouring 
matter permeates the tissue in such a way as to suggest diffu- 
sion from the latex vessels of the core. The colouring matter 
is not acted on by iron salts ; in a tannin cell the content turns 
blue, but the wall remains yellow. It is insoluble in alcohoL 
With 1 per cent, osmic acid the tannin content rapidly turns 
blue or black, but the walls darken only very slightly and 
slowly. The yellow colouration is probably due to the 
production of some decomposition product in the latex 
vessels ; its subsequent diffusion into the surrounding cells 
results in the staining of the cell walls. This is the first 
symptom of the change in the latex vessel content. Sections 
of nodular cortex showing very early stages have been 
obtained ; and these show the inception of nodule formation 
