characteristic tissue by which the seed can be identified; but where it happens that the seed is skinned before being roasted, it becomes necessary to seek for evidence of its identity, either in the condition of the cells or in the character of the starch, if any be present. It is not, however, always practicable to distinguish very clearly the particular kind of starch present, owing to the broken condition of the granules produced by torrefaction.

E

FIG. 17.-BEAN.
Tissues of Bean, magnified 50 diameters.

When a few grains of a sample containing a leguminous or other starchy seed are placed under the microscope, and a little iodine solution added, the particles of roasted starchy matter will appear of a more or less distinct purple colour.

Beans. The garden bean consists principally of very tough thick-walled cells, seen in mass at E, Fig. 17, filled with large starchgranules. These cells are generally oblong, and when crushed

they separate freely from each other, presenting the appearance of tough bags. The starch-granules are also oblong, and have a slit on one side resembling somewhat a grain of barley in miniature. The husk or skin of the bean is a dense thick integument, composed of transparent narrow cells, placed parallel with each other and perpendicularly to the seed. They are represented at A in Fig. 17. The tenacity existing amongst these cells is not easily overcome, but after long boiling with a few drops of caustic potash, the cells may be separated by a little pressure, and they then present the appearance of narrow transparent wedges with light brown centres, as seen at B. In addition to these, there occur other cells having somewhat the shape of dumb-bells; they are represented at c, and are highly characteristic. The inner skin of the husk consists of loose oval cells, as at D, each enclosing what seems to be a second cell, the interior of which is filled with dark granular matter.

Peas.-The structure of the pea is so nearly akin to that of the bean as to render it difficult to distinguish between them by means of the microscope. The skin is a tough thin integument, consisting of minute flat hexagonal cells resembling honeycomb, and resting upon a delicate colourless membrane composed of fine thin-sided cells somewhat larger than the hexagonal cells.

Drawings of the starches of beans and peas will be found in Part II. The wedge-like and dumb-bell-shaped cells, together with the starch-granules, furnish characteristics by which the presence of beans or peas in any sample of coffee thus adulterated can be with certainty identified.

Wheat, Barley, Rye, and Maize.—The microscopic structure of these and other cereals which are sometimes used as adulterants will be found and described in Part II.

Locust or Carob Beans.-The pod of the locust bean is com

F

posed of several very characteristic structures; these are shown in Fig. 18. A represents the epidermis, and в the coloured cells lying underneath, which are easily separated by slight friction. c and E, the third and fifth layers of the pod, consist of woody fibre, amongst which are scattered sclerogen cells. Rows of small round cells are also abundant, lying in a regular manner

along the sides of many of the woody cells. At D is represented the most characteristic structure of the pod. It consists of large, somewhat oval, cells, having so little cohesion that slight trituration suffices to separate them. These cells have a light brown colour, and are generally striated.

The structure of the seed of the locust bean is delineated in Fig. 19. At A, B, and C, the husk or skin is represented, and at D and E the substance of the seed consisting of thick-walled cells filled with oil-globules and minute starch-granules. These structures are very similar to those usually found in leguminous seeds.

The presence of the wedge-shaped cells, and of starch-granules in the seed, and the very marked structures in the pod, especially the large coloured cells, render the detection and identification of this adulterant comparatively simple.

Acorns.-The seed of the acorn is composed of thin-sided

oval, or oblong cells (seen at A, Fig. 20), with marks or dots on their sides, caused by the minute starch-granules with which the cells are filled. At в these starch-bags are represented B more highly magnified, and at c the starch-granules are seen bursting through the cells.

The skin of the acorn is a cellular membrane, containing bundles of spiral vessels, as seen at D, E, and F, the cells being very irregular in form.

Tissues of the Husk and Seed. A, D to K magnified 50 diameters, B and C magnified 150 diameters.

The

The shell of the acorn, which is but seldom ground up with the seed, consists of two parts, an inner and an outer. former of these is soft and easily broken up, and the latter hard and horny, so much so, in fact, as to resist all ordinary attempts to disintegrate it. The cells of the inner surface, shown at G, are oblong, and generally run in lines or rows. Those of the outer surface, seen at H, are minute and extremely dense, and are covered by a transparent epidermis, K and L, which is composed