PROGRESS OF MICROSCOPICAL SCIENCE. 235 



the latter stains the original cell wall of these thickened cells and 

 also the pores, rendering these latter very perceptible. This latter 

 reaction is probably not chemical but mechanical, the minute pores 

 retaining the dye longer than the exposed cell surfaces. The whole 

 of the other tissues of the bark, excepting the resin receptacula, it may 

 be noted, permanently stain with the logwood fluid. The general 

 shape of the thickened cells is ovate, but more or less globose ones 

 are frequent. Within the layers of stellate cells are many layers of 

 thin-walled parenchymatous cells containing various minute granules 

 of starch and other matters, some of which, apparently allied to 

 chlorophyll, stain intensely with magenta. Amongst these cells are 

 distributed very irregularly large receptacula, containing a light 

 yellow coloured oleo-resinoid substance. On removing this it is 

 found that the walls of the containing-cell are thin, imperforate, 

 that they stain intensely with magenta, and do not permanently stain 

 with logwood. That their walls are very thin is shown by their 

 slight action upon a selenite plate by polarized light; for when 

 freed from their contents they scarcely raise or depress the colour of 

 even the teint sensible film, the very delicate red-violet. With these 

 parenchyma cells are a few liber bundles, not many. The liber 

 proper forms the lighter internal surface of the B.P. description. It 

 is chiefly remarkable for the great number of sphaaraphides arranged 

 linearly among the liber cells, as seen in cross section, and apparently 

 composed of oxalate of lime. These are almost wholly confined to 

 the layer bounding the inner surface of the bark. The liber cells 

 are hollow, little thickened, and frequently contain minute granules 

 of starch and other granular substances. The medullary rays and 

 oblong or sub-cylindrical cells associated with the liber are not very 

 interesting. The cells of the medullary rays are nearly square, with 

 incomplete parietal adhesion, and contain considerable quantities of 

 minute starch granules, spherical or ovate, doubly refractive, and 

 giving a black cross. A large number of cells associated with these 

 square cells, and forming part of the medullary rays, contain, each 

 cell singly, sphaaraphides imbedded in a semi-granular substance 

 (probably semi-fluid when the bark is fresh) of apparently a saccha- 

 rine nature, and unless this be removed by maceration in water, and 

 subsequently alcohol, the polariscope and chemical reactions of the 

 crystals will be but feeble. In conclusion it may be remarked that 

 the structure of Canella alba bark is somewhat complex, but not 

 difficult of study to a microscopist of moderate experience, although 

 there are features, such as the nature of the contents of some of the 

 cells, notably of the liber cells and medullary rays, that are almost or 

 quite beyond the reach of present micro-chemical histology. Granati 

 Radicis Cortex. — Pomegranate Root Bark. — The cells of this bark are 

 altogether very different from either of tbe preceding, both as regards 

 size and shape. The external cells are small, sub-globose, and some 

 of them porous. The cells of the layers beneath, excluding certain 

 ligneous cells, are sub-cylindrical, thin-walled, and small in cross out- 

 line. Their contents are starch granules, very minute and sphasra- 

 phides, of which each cell contains one, imbedded in a substance of 



