Repository: UIHistories Project: Board of Trustees Minutes - 1886 [PAGE 205]

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197 of each family of plants wear clothes often of a very different pattern. The Pericarp of a grain of maize corresponds to the hard, thick shell of the hazelnut; to the fleshy, pulpy and succulent portion of the currant and gooseberry; to the combined edible portion and stony covering of the seeds of the plum, peach, cherry, etc.; to the pulpy and stony coverings of the walnut and butternut, and to the burrs of the buckeye and horse chestnut. In those fruits like the plum and peach, and also in those like the walnut, the stony covering of the kernel is the Endocarp and the pulpy covering the Epicarp. The Testa or outer covering of the seed proper (Fig. B, No. 10) is little developed, being composed of thin-walled, loosely-joined cells. It is here that the separation takes place when corn is hulled. As a rule, where the seed is covered with a hard or tough Pericarp, the Testa is insignificant, as in the hazelnut, walnut and stone fruits; where the Pericarp is fleshy and succulent, the Testa is hard and resisting, as in seeds of berries. The Envelope.—We now come to that curious envelope of gluten cells, called by some writers the embryonic envelope. Whether it is really a portion of the embryo, I have been unable to decide from the section that I have examined. The cell contents are much the same in structure and composition, being composed chiefly of nitrogenous and fatty substances, which are highly nutritious. According to M. Mege-Mouries, who has studied this envelope in the wheat, it contains a special ferment called cerealine, which possesses the property of rapidly changing starch to sugar. Payen and Persoz attribute this action to a nitrogenous substance called Diastase, while Saussure thinks it due to a soluble^ nitrogenous body in the gluten, called Muciden. It may be that an unorganized ferment, as variously described by these writers, aids in the process of germination in the seeds, as well as adding to its digestibility, but it needs further investigation to establish the fact. Starch.—Within this envelope of gluten cells is a framework of thin-walled cells of cellulose filled with irregular but characteristic six-sided (in outline) grains of starch (No. 4, figs. A and B). This part of the seed, called the Endosperm, is largely developed in the grasses and cereals (Graminece) and is a very important food product, starch, of which it is almost wholly composed, being the chief constituent of all our vegetable foods. Indian corn contains 68 per cent, of starch. Different seeds have characteristic forms and sizes of starch grains, many easily identified under a powerful microscope, Relation of Parts.—The relation of the various parts of the Embryo (Nos. 5, 6, 7, 8, 9, figs. A, B) of maize and other grasses has puzzled many botanists and is still a subject of controversy. Suffice it to say at present that 7 is primary root, 8 its root-sheath, 6 the Plumule or stem end of the plant, 5 the Scutellum, and 9 a row of cells much like those surrounding the Endosperm, but they are smaller. The Scutellum surrounds the rest of the Embryo, and according to Sachs, when germination takes place remains within the Endosperm as an organ of absorption until the Endosperm is consumed. The cells of the Scutellum (Fig. B, 5) are spherical and thick-walled, and are filled with nitrogenous matter similar in