6 
THE FUNCTION OF TANNIN. 
more or less completely tlie whole protoplasmic body of 
the cell. Often there is no contraction of the protoplasmic 
body, and the whole contents of the cell, excepting the thin 
primordial utricle closely applied to the cell-wall, are highly 
coloured (e.g ., leaf and cortical cells of Prunus Laurocerasus, 
Hex aquifolium ). Where oil drops are present, e.g ., in Ilex 
aquifolium, these, in such cases, show brightly through the 
yellow-brown mass.* 
In the second case, where the cells contain large quantities 
of starch, as met with in the medullary rays of the wood, the 
cells of the pitli-crown, many cells, isolated or in a reticulum, 
of the central pith, and the wood cells (where tannin is 
comparatively infrequent), the tannin, originally in solution 
in the cell-sap, becomes, as the latter is displaced by the 
accumulating starch grains, firstly more and more concent¬ 
rated, penetrates often, as already noted, the starch grains 
themselves, and when treated with potassium bichromate 
commonly the whole mass of the cell-contents collects into one 
very dark brown bail, in which the starch grains are barely 
or not at all distinguishable ; sometimes it forms an irregular 
brown granular-looking reticulum, in the meshes of which 
the starch grains can easily be seen. 
Wigand is partially correct when he says that when a 
plant contains tannin and starch, the two are usually not 
only in the same tissues, but also in the same cells ; but he 
is far from correct when he says that they are not, as a rule, 
present simultaneously. 
On the other hand, in many cells, particularly in those 
which in spring have been emptied of their starch, but also 
in many cortical cells, particularly in the “ exhausted” plants 
hereafter spoken of, the potassium bichromate does not form 
these clear masses with the tannin, but instead we get 
irregular collections of blackish brown disintegrated looking 
fragments or small lumps, especially collecting round the 
outer parts of the cell-lumen, leaving the centre quite free. 
This difference is probably significant. 
* During life, probably, the protoplasm is not so freely permeable 
to tannin as is generally assumed. After death, and use of iron 
reagents, I have sometimes found the nucleus in tannin-containing 
cells, as well as in the neighbouring cells, beautifully stained from 
infiltration of tannin, e.g., in the rhizome of Botrychium lunaria. By 
soaking sections of cellular tissue, free of protoplasm, e.g., sections 
from a fallen leaf-stalk, in a solution of tannin, and then testing with 
iron salts, the cell-wall, too, is often well stained, a phenomenon which 
I have not noticed during life. This is probably the explanation of 
Hartig’s, “ Wandungszustand ” of tannin in Salisburia. 
