THE FUNCTION OF TANNIN. 
307 
bildenden Zellen bis zum friiliesten Zustande derselben auf- 
warts, die Korner in kaltem Wasser olme Quellungsers- 
clieinungen leicht loslich sind, und von Eisensalzlosiingen 
scliwarz, zugleicli aber aucli durcli Jodlosung wie Starke 
blau gefarbt werden.” (1. c., p. 119). 
Quercus pedunculata I have carefully examined at different 
periods through the late autumn, winter, and succeeding 
spring and summer. Throughout the winter the distribution 
of the tannin is as follows ( e.g ., in a three year old stem):— 
In cortex, in large numbers of cells, each with a large mass 
of tannin (i.e., diffused); bast, with small amount; bast rays, 
every cell filled with a granular, turbid-looking mass; wood 
ray cells, with abundant tannin, as have also many of the 
cells of the pitli-crown, and fewer of the inner pith-cells. 
Investigation at the same time of the contents of the stem 
by means of iodine reagents, and particularly by clilorzinc 
iodine, shows the following distribution of starch :—Cortical 
tissue and bast very little ; bast rays none, or only a trace ; 
wood rays quite full, commencing abruptly at the cambium 
layer (the starch in these cells stains at first very light 
reddish violet alike with iodine and with chlorzinc iodine). 
Wood fibres of all years in parts densely crowded, not only in 
the elongated wood-cells, with straight or oblique partitions, 
but also in many of the true libriform fibres with fusiform 
overlapping ends, and this especially the case in the inner¬ 
most ring of wood; pith-crown cells full, as also many cells 
of the inner pith. 
The use of chlorzinc iodine shows that m the coloration 
of the starch of the wood there is a large amount of red, 
overcoming in parts the blue ; the whole contents of the soft 
bast show also a reddish tinge. The medullary rays I have 
already referred to ; the starch in many of the pith-crown 
cells stains at first reddish with a voilet tinge, and where a 
grain from these is accidentally isolated it can be seen to be 
often of a pure magenta-red, or with a brownish tinge. In 
some cells often are grains which are red and others blue. 
In some cells all grains have a blood-red colour, in other 
cells all are more or less violet. 
Iron salts showed in many isolated pitli-crown cells, and 
in most of the wood-ray cells, grains, like in size and form to 
starch grains, but coloured of a cloudy blue tint. Sections 
placed in oil, after the fashion of Hartig, showed the same 
granules, no more and no less, and with the same reactions. 
Repeated and careful examination showed that in no case 
did this so-called Gerbmelil of llartig occur, except where 
