The medicinal plants containing inulin are dandelion, chicory, elecampane, pyrethrum, and burdock. Plate 77, Figs, 1 and 2 show masses of inulin in dandelion and pyrethrum. In these plants the inulin occurs in the form of irregular, structureless, grayish-white masses (Plate 77). In powdered drugs inulin occurs either in the parenchyma cell or as irregular isolated fragments of variable size and form. Inulin is structureless and the inulin from one plant cannot be distinguished microscopically from the inulin of another plant. For this reason inulin has little or no diagnostic value. The presence or absence of inulin should always be noted, however, in examining powdered drugs, because only a few drugs contain inulin. When cold water is added to a powder containing inulin it dissolves. Solution will take place more quickly, however, in hot water. Inulin occurs in the living plant in the form of cell sap. If fresh sections of the plant are placed in alcohol or glycerine, the inulin precipitates in the form of crystals. MUCILAGE =Mucilage= is of common occurrence in medicinal plants. Characteristic mucilage cavities filled with mucilage occur in sassafras stem (Plate 66, Fig. 2), in elm bark (Plate 66, Fig. 1), in althea root, in the outer layer of mustard seed, and in the stem of cactus grandiflorus. In addition, mucilage is found associated with raphides in the crystal cells of sarsaparilla, squill, false unicorn, and polygonatum. When drugs containing mucilage are added to alcohol, glycerine, and water mixture, the mucilage swells slightly and becomes distinctly striated, but it will not dissolve for a long time. Refer to Plate 79, Fig. 6. Mucilage, when associated with raphides, swells and rapidly dissolves when added to alcohol, glycerine, and water mixture. The mucilage is, therefore, different from the mucilage found in mucilage cavities, because it is more readily soluble. [Illustration: PLATE 77 INULIN (_Inula helenium_, L.) 1. Inulin in the parenchyma cells of dandelion root. 2. Inulin from Roman pyrethrum root (_Anacyclus pyrethrum_, [L.] D. C.). ] 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