36 CINCHONA BARKS. 
The originally collenchymatous outer bark, situated beneath the 
cork, is built up of cells of considerable size, which are more or 
less extended in a tangential direction (Plate VII, A. C. 0). The 
uniformity of this tissue (without considering the interior cork for- 
mation) is thereby interrupted, in that its often coarse, porous cells 
become, either singly or in large numbers, sclerotic. Such stone- 
cells (Plate VII, C. k) are, in the dried bark, either empty or filled 
with a crystalline powder of calcium oxalate, or contain a reddish- 
brown, solid, occasionally granular substance, which, without suffi- 
cient foundation, has been designated as resin. The stone-cells 
(sclerotic cells) vary in their form without regularity, so that it must 
be regarded as superfluous to distinguish them as cubical cells, as 
spherical, or upon the transverse section tangentially extended 
stone-cells. A discrimination according to their contents, as crystal- 
cells and resin-cells, is likewise of no greater importance. In the 
direction of the axis, the stone-cells of the Cinchona barks exhibit 
no considerable extension. They appear in the bark, either scat- 
tered singly or united in groups, but never representing actually 
closed circles of large dimensions, as in so many other barks: ¢. g., 
that of Guaiacum officinale,* Quassia amara,? and Strychnos Nux 
vomica.? In many Cinchona barks, the stone-cells are uniformly 
wanting: e. g., in the Calisaya and the red bark; in others they 
occur sparingly, and in many they are found abundantly, and also 
in the bast, as, for instance, in Cinchona latifolia, 
On the boundary of the bast, but always only on the inner side 
of the parenchyma of the outer bark, isolated ducts of very con- 
siderable size are frequently observable, which, upon a trans- 
verse section (Plate VII, A. p), present a circular or tangentially 
extended outline, and in circumference, but not in the thickness of 
the walls, surpass the neighboring parenchyma cells. In the larger 
diameter they frequently attain over 200 micromillimeters (C. succi- 
rubra), in C. boliviana, even more than 500, but are also often 
diminished to less than from 40 to 50 micromillimeters. 
On a longitudinal section, these mk tubes or lacticiferous ducts 
do not appear extended in length; their obtuse ends are closed, 
and they are usually isolated, or from two to three arranged in a 
row before the last bast-wedges, without, however, having any defi- 
nite relation to the latter, Ona transverse section, the lacticiferous 
ducts therefore form a but slightly regular, sometimes repeated, 
* Compare Fliickiger, Pharmakognosie, second edition, 1882, p. 453. 
* Ibid, p. 459. 
* The same work, first edition, 1867, p. 427. Moller, Anatomie der Baumrinden, 1882, 
pp. 162, 419. 
