a. Lower epidermis.

b. Trichomes.

c. Pollen grains.

Fig. 4. ACONITUM. Leaf.

d. Parenchyma cells of stem.

e. Sclerenchyma cells.

f. Upper epidermis.

5. (Fig. 5.) ACONITE ROOT. U.S.

Fl. ex. 40. Tinct. 60.

The roots of Aconitum napellus L. Ranunculaceae.
Dry, slightly starchy or mealy feel.

Light brown.

Odor faint, recalling horseradish when moist.

Taste sweetish, very markedly and persistently acridly pungent; acridity especially marked in the fauces. Benumbing effect.

Predominating elements are derived from the more or less broken, large, rather thick-walled, essentially isodiametric closely united parenchyma cells filled with compound starch granules. A few slightly brownish, essentially rectangular only slightly elongated, rather thin-walled, very porous sclerenchyma cells, which generally occur singly, rarely in twos. Some porous ducts and tracheids; spiral ducts rare.

Starch granules singly, in twos, fours and in aggregates of from five to seven; hili distinct in the larger granules, centric; single granules 5μ to 15μ; cross bands quite distinct, broad, right angled. There should be no thick-walled sclerenchyma, no true bast, and vascular tissue should be sparingly present.

Ash about 5 per cent. Impurities should not exceed 5 per cent. Deep yellow with potassium hydrate solution. Deep red with concentrated sulphuric acid.

Among the possible adulterants are horseradish (simple, oval to elliptical starch granules, 5μ to 15μ, with very indistinct hili and lamellations); A. Fischeri, (starch granules mostly simple and in twos and the aggregates of five to nine). Single granules somewhat larger than in A. napellus and some of the sclerenchyma cells considerably elongated; Japanese aconite (sclerenchyma cells wanting). Suspect other species and varieties of aconite, also the use of exhausted powder, crowns and stem parts (fibrous tissue excessive and a few 2- to 5-celled trichomes). Suspect roots from other groups of plants.

Fig. 6. ACONITUM FISCHERI.

a. Sclerenchyma cells, nearly colorless.

b. Sclerenchyma cells, nearly colorless.

c. Sclerenchyma cell from cork layer, deep reddish brown.

d. Parenchyma cells bearing starch, transverse view.

e. Parenchyma cells, longitudinal view. Starch granules mostly simple, rarely two and three compound. Large number of aggregate granules, many of which become separated in powdering showing the pentangular simple granules. f. Ducts.

The distinguishing histological characteristics between A. Napellus and A. Fischeri are: In A. Fischeri the cell-walls are as a whole thinner, particularly of the parenchyma cells. Sclerenchyma cells are more abundant and more elongated. Starch granules mostly simple with many aggregate granules and polygonal simple granules.

It would be difficult to detect admixtures of the two roots in powdered form.

Fig. 7. AGAR. a and b, two species of dictams which are constantly present in agar. The larger species is Arachnodiscus Ehrenbergii Bail. cand d, mucilaginous tissue elements of agar as they appear in the commercial article.

6. (Fig. 7.) AGAR. Agar. U. S.

Granulated.

The bleached and specially prepared seaweeds belonging to the Rhodophyceae, represented by species of Gracilaria and Gelidium. Hard granular when dry; mucilaginous when moist.

Pale brownish color.

Odorless when dry, seaweed odor when moist.

Tasteless, mucilaginous.

The process of preparing the seaweed for the market does not entirely destroy the cell structure, and in even the highest and purest grades of commercial agar cell remnants and the siliceous skeletons of diatoms may be found.

The ash of a good quality of commercial agar should not exceed 4 per cent.

Agar is seldom adulterated. It may be mixed with other seaweeds and it has been mixed with starch and cereal, although this is of rare occurrence. Agar is used as an adulterant, being occasionally added to jellies and as a filler to ice cream.