In cubeb and pepper is aggregate starch. Colocynth contains many single and double spiral vessels.
Bitter orange contains solitary crystals and spongy parenchyma.
When studying fruits we must consider the nature of the epicarp cells—whether simple or modified as papillæ or hairs; the form and structure of the mesocarp cells; the number, size, and structure of the vascular bundle; the size and number of the secretion cells or cavities; the number of layers and the structure of the endocarp cells; the number of layers of stone cells—when present; the color and width of the spermoderm layer; the structure and cell contents of the endosperm cells; the nature of the embryo cells, and the nature of the cell contents.
CHAPTER IX
SEEDS
Seeds are very variable in structure, so much so, in fact, that scarcely any two seeds have a similar structure. It is necessary, therefore, when examining seeds, to compare the structure of the seed under examination with authentic plates or with the section of a genuine seed. The layers of the seed are the spermoderm, perisperm, endosperm, and embryo. In some seeds the spermoderm forms the greater part of the seed; in others the perisperm is greatest in amount; in still others the cotyledons make up most of the seed, as in the mustards. The cells forming these different layers differ in form, structure, and number; therefore it is not difficult to distinguish and to differentiate between the different seeds when viewed as a section or as a powder. Almond is studied because it has most of the layers and cells found in seeds.
SPERMODERM
The spermoderm is the thin, brown, granular-appearing skin of the almond. The layers of the spermoderm are the epidermis, the hypoderm, the middle layers, and the inner epidermis.
The epidermis consists of radially elongated, thick-walled stone cells which occur alone or in groups of two or more, but seldom as a continuous layer. The upper or outer part of the stone cells is non-porous, but the inner walls are strongly porous (Plate 123, Fig. 1).
The hypoderm. The cells forming the hypoderm are compressed, the wall structure is practically indistinguishable, and the whole mass is reddish brown (Plate 123, Fig. 2).
Occurring in this brown layer are several vascular bundles (Plate 123, Fig. 3).