The elements of botany for beginners and for schools by Gray Asa 1810-1888

Author:Gray, Asa, 1810-1888
Language: eng
Format: epub, pdf
Tags: Botany
Publisher: New York : American Book Company
Published: 1887-03-25T05:00:00+00:00

SECTION 15.]

EMBRYO.

127

3S6. The Kernel, or Nucleus, is the whole body of the seed withiu tlie coats. Ill many seeds the kernel is all Embryo; in others a large part of it is the Albumen. For example, in Fig. 423, it is wholly embryo; in Fig. 422, all but the small speck (^(j) is albumen.

387. The Albumen or Endosperm of the seed is sufficiently characterized and its ofHcc cxphiiued in Sect. 111., 31-35.

388. The Embryo or Germ, wliich is the rudimentary plantlet and the final result of blossoming, and its development in germination have been extensively illustrated in Sections II. and 111. Its essential parts are the Radicle and tlie Cotyledons.

389. Its Radicle or Caulicle (the former is the term long and generally used in botanical descriptions, but the latter is the more correct one, for it is the initial stem, wliich merely gives origin to the root), as to its position in the seed, always points to and lies near the niicropyle. In relation to the pericarp it is

Superior, when it points to the apex of the fruit or cell, and Inferior, when it points to its base, or downward.

390. The Cotyledons have already been illustrated as respects their number, — giving the important distiuction of Dicotyledonous, Polycotyledonous and Monocotyledonous embryos (36-43), — also as regards their thickness, whether _/o/2tf^^o«s or _/^s/^^;

and some of the very various shapes and adaptations to the seed, have been figured. They may be straight, or folded, or rolled up. In the latter case the cotyledons .may be rolled up as it were from one margin, as in Calycanthus (Fig. 424), or from apex to base in a flat spiral, or they may be both folded {plicate) and rolled up (j'onvolute), as in Sugar j\Iaj)le (Fig. 11.) In one very natural family, the Crnciferae, two ditierent modes prevail in the way the two cotyledons % '■'■# Vy are brought round against the radicle. In one series they are

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