In coarse-powdered bark and other mucilage containing drugs the mucilage masses are mostly spherical or oval in outline (Plate 66, Figs. 2 and 3) the form being similar to the cavity in which the mass occurs.
Acacia, tragacanth, and India gum consist of the dried mucilaginous excretions.
HESPERIDIN
Hesperidin occurs in the epidermal cells of short and long buchu. It is particularly characteristic in the epidermal cells of the dried leaves of short buchu. In these leaves the hesperidin occurs in masses which resemble rosette crystals (Plate 54, Fig. 1).
Hesperidin is insoluble in glycerine, alcohol, and water, but it dissolves in alkali hydroxides, forming a yellowish solution.
VOLATILE OILS
Volatile oils occur in cinnamon stem bark, sassafras root bark, flowers of cloves, and in the fruits of allspice, anise, fennel, caraway, coriander, and cumin.
In none of these cases is the volatile oil diagnostic, but its presence must always be determined.
When a powdered drug containing a volatile oil is placed in alcohol, glycerine, and water mixture the volatile oil contained in the tissues will accumulate at the broken end of the cells in the form of rounded globules, while the volatile oil adhering to the surface of the fragments will dissolve in the mixture and float in the solution near the under side of the cover glass. Volatile oil is of little importance in histological work.