ON THE ANATOMY OF DRUGS. 
547 
The number of plants whose roots are esteemed their most serviceable part is 
very large, indeed the list of those recognized as officinal is even longer than 
that of barks. It would be almost impossible to define what is understood as a 
“root ” in any positive characters not equally applicable to the stem, but for 
pharmaceutical purposes the term may be taken to imply the descending axis of 
a plant. Many Exogenous plants have roots with a distinct separable bark, 
indeed, in at least two familiar instances, those of mezereon and pomegranate, this 
is the active medicinal portion. Many likewise, such as Pareira Irava^ have the 
wood}?- portions arranged in the most marked, annual, concentric rings, traversed 
by medullary rays. Probably the only well-defined distinction a physiologist 
could lay down between the ascending and descending axis of a plant, apart 
from the direction of growth, would be, that the former does and the latter does 
not produce leaf-buds; characters affecting the external relations rather than 
the minute anatomy of either. Let us take two or three dissimilar examples 
and note their peculiarities. 
The structure of rhubarb* root has occupied the attention of many authors 
seeking to obtain histological characters by which the origin and value of com¬ 
mercial samples might be estimated. The results, however, are only of bo¬ 
tanical interest and have but little value in a commercial sense, for there is 
scarcely a single peculiarity of minute structure in the finest specimens of the 
“ Russian ” variety not shared, to a greater or less degree, by the comparatively 
wortliless product of our own gardens. We do not wish to imply that the roots 
are alike, but that the differences are rather in their sensible physical properties 
than in their microscopic features. 
The general characters of Russian rhubarb are well described by Pereira. 
The external surface of the trimmed root is not uniform, but shows, when the 
yellow dust is removed, a dark reddish-white ground with lighter coloured lines 
or veins crossing each other diagonally and with considerable regularity in 
their arrangement. The reticulated appearance thus produced may be seen in 
any good specimen. The mass of the root is composed of ordinary cellular 
tissue (parenchyma) with woody bundles distributed unevenly through it, and here 
and there confused groups of annular and spiral vessels. On the surface of the 
root and also at irregular intervals in the transverse section, but chiefly near the 
periphery, may be observed little, darker-coloured, circular spots, which when 
magnified are seen to consist of sinuous lines radiating from a centre. Crystal¬ 
line tufts of oxalate of lime, common in every portion of the root, are particu¬ 
larly abundant in cellular tissue of the radii. The raphides occur in cells proper 
to them, and may be studied in English rhubarb as well as in Russian, but 
in some samples of the latter they amount to from thirty to forty per cent, of 
the whole w'eight of the root. 
It is therefore chiefly in such peculiarities as weight, colour, fracture and taste 
that means of diagnosis of the quality of the root must be sought. 
Of very different nature is the common licorice-root [Glycyrrldza glahra). 
In the transverse section we have a type of structure very frequent amongst 
exogenous herbaceous plants. There is no true bark, but instead, a somewhat 
closer packing of the thin-walled cells in the epidermal region, which might, 
under favourable circumstances, be developed into a corTy layer. A wider 
cellular zone traversed by bast fibres follows, and then a narrow well-defined 
ring of cellular tissue, answering to the cambium layer. Between this and the 
small central circle of pith lies the woody zone, consisting of irregularly grouped 
wedges of fibro-vascular tissue, separated by medullary rays. The medullary 
rays are unusually broad, and are conspicuous almost to the circumference of the 
section. But the most remarkable fact is one first pointed out, we believe, by 
our friend INIr. Schacht, in a very careful and accurate paper read before the 
Bristol Microscopical Society (March, 1857) and confirmed by Dr. Berg’s inde- 
