292 
PHYSIOLOGY. 
BOOK II. 
shades, from claret colour to the deepest violet. In those 
places where the section was not more than a single cell in 
thickness, a difference between the fibres in the above-men- 
tioned layers was visible, inasmuch as those of the under 
side of the leaf (the thickest), even where they were most 
deeply coloured, did not appear of a pure violet colour, but 
redder, somewhat as if there had been a slight addition of 
orange. These fibres were also evidently less tumid, and the 
boundaries were more clearly defined. Those in the middle 
of the leaf, on the contrary, appeared quite gelatinous, and 
were coloured of a light blue. The membrane of the cells 
was in all cases clear as water, and colourless. This was not 
all : those cells which contained no spiral fibres, and which 
before, when magnified 230 times, appeared to consist of quite 
simple walls, even those of the green parenchyma, appeared 
now completely pitted; the primitive membrane and its pits 
were clear as water, and colourless, whilst the pits of the 
thickening layer were of a violet colour. 
“ III. I now took for comparison a woody stalk of Rosma- 
rinus officinalis, and treated it in precisely the same manner. 
The result differed slightly from the above. Tlie cells of 
the pith are here very thick-sided and pitted, as are also the 
exterior cells. The wood consists of the medullary sheath, 
of spiral vessels, and of prosenchymatous cells, the walls of 
which are just like the woody cells of very young coniferous 
wood. Here, in every part except the youngest annual rings, 
the original membrane (even of the spiral vessels) was not 
coloured, whilst those parts superposed, and even the spiral 
fibres, were deep orange. The cells of the youngest annual 
ring, on the contrary, appeared slightly pitted and very pale 
blue. 
“ IV. A species of Pelargonium, when submitted to the 
same action, gave the same results, only that the thin-walled 
but pitted exterior cells were also coloured blue. 
‘‘ V. In the Teltow Turnip and Carrot, the primitive walls 
of the cells remained colourless ; the incrusting layers of the 
same became blue ; whilst, on the contrary, the fibres of the 
spiral and reticulated vessels became deep orange. 
“ VI. The spiral fibres, in the cells of a leaf of Oncidium 
