CHAP. I. 
ELEMENTARY ORGANS. 
298 
altissimum, which had been preserved for seven months in 
weak alcohol (of about 30°), were coloured orange. The 
spires here consist, however, of two parts, which on the plane 
of the section could be easily distinguished, as in Arundo 
Donax ; and I imagine that the spire in Pleurothallis consists 
only of the inner original fibre. I was not able to institute 
any experiments with fresh leaves of this plant, and have 
therefore not been able to decide this question with certainty. 
The original cellular membrane remained here, as in the 
first-mentioned cases, colourless, and the layers of increase 
became blue. 
‘‘ VII. Opuntia monacantha gave the same results. In all 
the cells which were completely converted into wood, the 
additional layers, whether spiral or pitted, became of a deep 
orange colour, those of the pith and bark blue, and the 
primary cellular membrane still remained clear as water. 
“ An Echinocactus gave the same result. 
“ VIII. The wood of Betula alba and Populus tremula, 
when submitted to the above manipulation, showed nothing but 
pitted formations, the primitive membrane of which remained 
colourless, whilst the layers of increase were coloured dark 
orange. 
“ IX. A five years’ old shoot of the trunk of Pinus silvestris 
gave, as regards the original walls of the cells, confirmation of 
the former constant results. The layers of increase were 
coloured orange, the cells of the bark and the youngest an- 
nual rings light blue. 
‘‘ It is of course to be understood, that, by comparative 
experiments on all these plants, I had previously satisfied 
myself of the absence of starch in the cells in question. 
‘‘ The foregoing, though only preliminary experiments, 
seem to indicate the following results : — 
“ I. Vegetable tissue consists of three distinct chemical 
substances : — 
a. The original membrane of the cells. 
h. The primary layers upon this, 
c. The secondary layers. 
“ 2. The first substance (1. a.) undergoes no apparent 
change by a short boiling in caustic potash. 
u 3 
