tubes or ducts, disposed more thickly in concentric circles about the fortieth of an inch apart, or forming a single circle. Radiating from these are delicate medullary rays. When gathered in the spring or early summer, the centre is pierced by a light pith or a small cavity. The root when dry is brittle, and snaps readily, giving a clear, smooth fracture. As found in the market there are few, if any, fibres attached, although when fresh the root is well supplied with secondary roots, but as they are very brittle when dry, they do not long remain attached." Its microscopical characters are: First, an epidermis of a single row of cells which adheres but loosely to the root; next, a layer of cork varying from four to seven cells in thickness in the specimens examined, the outer rows of which have strongly thickened walls,

APOCYNUM ANDROSEMIFOLIUM, TRANSVERSE SECTION.-a, Cork cells; b, cortex; c, bas cells; d, cambium; e, wood, f, dotted ducts; g, bast-like cells; h, pith.

the inner, less so, and constituting a layer of cork cambium, or meristem. These cells are separated by a tolerably well-defined boundary from the inner cortical tissue which occupies in general about one-half the diameter of the root. The cells composing this structure are in the outer portion of the zone, quite irregular in shape and size, assuming greater regularity, and decreasing somewhat in size toward the centre, where they approximate to a spherical form. Large lactiferous. ducts are found in abundance in this portion of the root, and the cells of this tissue are generally well filled with starch-granules, and when

fresh, protoplasm. This zone is limited, interiorly, by a narrow line of cambium, the cells of which are exceedingly difficult to distinguish after the specimen has been dried, and this in turn is succeeded by the medullary sheath, or woody tissue of the root, which, with the exception of a few cells of pith in the centre, occupies the remainder of the semi-diameter of the root. The tells of this tissue are lignified (or woody), and it is composed of three histological elements, comprising large dotted ducts, medullary rays, and prosenchyma. The dotted ducts are numerous and plainly visible to the naked eye, but otherwise present no peculiarity. The medullary rays, springing from the central pith and from the annual rings, extend plainly half or two-thirds through the inner bark, where they lose themselves in the general tissue, and are composed, transversely, of one, and in their central portion frequently two rows of cells, and in their vertical direction of an indefinite number, while the medullary cells are, in the transverse section of the ray, elongated, and vertically are nearly round. The prosenchymatous cells present no features requiring description.

The starch of apocynum cannabinum, as previously stated, is found in the cells of the inner bark. The granules are exceedingly irregular, both in size and shape; they are in fact sufficiently so to make this feature somewhat characteristic. Several successive measurements of twenty grains, taken so as to include, as nearly as possible, all in a given space, gave an average long diameter of .0082 millimeter and .0074 millimeter short diameter. The extremes, so far as measured, were .014 millimeter maximum, and .0025 millimeter minimum. In shape, the more perfect granules are nearly oval, others approach angularity, or are variously contorted, while the smaller grains are nearly round.

In the centre of the woody column are a few nearly spherical pithcells. Bast-cells, although a prominent feature in the bark of the stem, were not observed in any of the specimens examined.

"Apocynum androsæmifolium has a long, running root. When dry it is contorted, frequently having the woody remains of its stalks attached. It is shrivelled longitudinally, and often marked by transverse fractures, that extend through the bark and show the white woody centre. Occasionally the bark scales off. The root breaks with difficulty, its central part being woody. Externally, the bark is dark brown, white upon its inner surface, and readily separates from the central or ligneous part of the root; it is very bitter. The central part of the root is smooth and firm, bends before breaking, and usually requires considerable twisting before the woody fibres give way. Attached to the root are rootlets, not very plentiful, which bear a general resemblance to the main root, their central portion being woody, and covered by a brown epidermis." The root of apocynum andro

sæmifolium presents the following histological characters: First, an outer layer of cork, usually from three to six cells in thickness; next, a zone of cortical tissue made up of irregularly shaped cells containing starch, this tissue occupying generally about one-eighth the distance from cortex to centre of the stem. The inner portion of this zone contains many bast-cells, the walls of which are strongly thickened; they are arranged in groups, are quite regular in size and form when examined in transverse section, and from this view show, like starch-grains, a cross under polarized light. The successive layers of their walls, also, show as well-marked striæ. Numerous intercellular

FIG. 96.-APOCYNUM CANNABINUM, VERTICAL SECTION.-a, Cork cells; b, cortex; c, lactiferous ducts; d, cambium; e, wood; f, dotted ducts; g, pith.

FIG. 97.-APOCYNUM ANDROSEMIFOLIUM, VERTICAL SECTION.-a, Cortex; b, cork-cells; c, bastcells; d, cambium; e, wood; f, dotted ducts; g, pith; h, bast-like cells.

spaces are seen in this portion of the cortex. Lying next this tissue, which may be designated as liber, is a narrow ring of cambium, somewhat more prominent than the same structure in apocynum cannabinum, but in the dried root somewhat difficult to resolve into its cellular elements. It appears, however, to be, when fresh, made up of very delicate, thin-walled, nearly spherical cells; or, in other words, it presents no peculiarities distinguishing it from cambium tissue in general. The woody portion of the root succeeds the cambium, and is, as in apocynum cannabinum, made up of prosenchyma and dotted

ducts, interspersed with medullary rays; it is considerably narrower, proportionally, than in its related species, the pith occupying a correspondingly larger space. None of its cells are sufficiently marked to present any distinctive points between the two that otherwise would be of value in the examination of the drugs when finely ground or powdered. The pith-cells are large and very irregular in form and size. Bundles of elongated cells with strongly thickened walls are found in this portion of the root. The starch in this species is exceedingly small and might easily be overlooked unless highly magnified. The granules are tolerably uniform in shape, being generally

nearly round or oval, and are far more uniform in size than in the species first described. An average of twenty measurements gives a mean diameter of .00498 millimeter. The largest measured was .0075 millimeter, the smallest .00375 millimeter in diameter. The differences between the starch-granules of these two species of apocynum are so great as to render their distinction by a mere microscopical inspection an easy matter, while the peculiar bast-cells of apocynum androsæmifolium afford an additional feature of value, and the pharmacist familiar with the microscopic appearance of the drugs could determine which of the two was offered, at a glance. The entire operation of mounting the powdered drugs on glass slips, and making such a comparison, should not exceed five minutes. Few of us are so busy that this brief period cannot be spared. The method is applicable to nearly all the powdered drugs of vegetable origin that we use, and the results of such an examination are, in this class of drugs, more reliable and certain than any other method affords. I may be within the limits of reason in expressing the belief, as well as the desire, that a microscope will, in the near future, be regarded as essential to a

pharmacy as a test-tube rack now is, and that the ability to use it will be ranked among the ordinary qualifications of the "drug clerk."

NOTE. In Fig. 98, ten lines of the appended scale (Fig. 100) are equal to one one-hundredth millimeter, and in Fig. 99, thirteen lines are equal to one one-hundredth millimeter. By comparison with a metric scale it will be seen that one is magnified about 650, the other about 800 diameters.

Figs. 96 and 97 are drawn to the same scale, each being magnified about 20 diameters. Figs. 94 and 95 are not drawn to scale. The specimens from which these examinations and drawings were made were furnished by Professor J. U. Lloyd, of Cincinnati,

AN INSTANCE OF ATAVISM IN CYPRIPEDIUM
SPECTABILE.*

BY PROFESSOR E. S. BASTIN.

ONE of the strongest proofs of the theory of descent is derived from the fact of atavism, that is, of the occasional reversion of an organism to a primitive or more generalized ancestral type. So interesting and instructive are facts of this kind, and so likely are they to throw new light on structures otherwise difficult to understand, that it seems of importance to science that every fact of the kind be carefully noted. An interesting case in point that came under my observation last June, viz., a monstrosity in a flower of Cypripedium spectabile, seems to me of such peculiar interest that I venture to bring a somewhat detailed description of it before your honorable society.

When botanizing with my class in the pine barrens at the southern end of Lake Michigan, a region by the way that deserves to rank with the pine barrens of New Jersey for the interesting character of its flora, a real botanist's paradise, we found the Cypripedium spectabile very abundant. It is safe to say that our little party of eight or ten gathered in a short time from five hundred to six hundred specimens of this beautiful flower, and we might have had twice or thrice as many if we could have carried them. A more enthusiastic group of botanists I think I have never seen than we were that day,

Read at the Fifth Session.