Section Xi. Ovules.

317. =Ovule= (from the Latin, meaning a little egg) is the technical name of that which in the flower answers to and becomes the seed.

318. Ovules are naked in gymnospermous plants (as just described), in all others they are enclosed in the ovary. They may be produced along the whole length of the cell or cells of the ovary, and then they are apt to be numerous, or only from some part of it, generally the top or the bottom. In this case they are usually few or single (solitary, as in Fig. 341-343). They may be sessile, i. e. without stalk, or they may be attached by a distinct stalk, the FUNICLE or FUNICULUS (Fig. 340).

319. Considered as to then position and direction in the ovary, they are

Horizontal, when they are neither turned upward nor downward, as in Podophyllum (Fig. 326),

Ascending, when rising obliquely upwards, usually from the side of the cell, not from its very base, as in the Buttercup (Fig. 341), and the Purslane (Fig. 272),

Erect, when rising upright from the very base of the cell, as in the Buckwheat (Fig. 342),

Pendulous, when hanging from the side or from near the top, as in the Flax (Fig. 270), and

Suspended, when hanging perpendicularly from the very summit of the cell, as in the Anemone (Fig. 343). All these terms equally apply to seeds.

320. In structure an ovule is a pulpy mass of tissue, usually with one or two coats or coverings. The following parts are to be noted, viz.--

KERNEL or NUCLEUS, the body of the ovule. In the Mistletoe and some related plants, there is only this nucleus, the coats being wanting.

TEGUMENTS, or coats, sometimes only one, more commonly two. When two, one has been called PRIMINE, the other SECUNDINE. It will serve all purposes to call them simply outer and inner ovule coats.

ORIFICE, or FORAMEN, an opening through the coats at the organic apex of the ovule. In the seed it is Micropyle.

CHALAZA, the place where the coats and the kernel of the ovule blend.

HILUM, the place of junction of the funiculus with the body of the ovule.

321. =The Kinds of Ovules.= The ovules in their growth develop in three or four different ways and thereby are distinguished into

Orthotropous or Straight, those which develop without curving or turning, as in Fig. 344. The chalaza is at the insertion or base, the foramen or orifice is at the apex. This is the simplest, but the least common kind of ovule.

Campylotropous or Incurved, in which, by the greater growth of one side, the ovule curves into a kidney-shaped outline, so bringing the orifice down close to the base or chalaza; as in Fig. 345.

Amphitropous or Half Inverted, Fig. 346. Here the forming ovule, instead of curving perceptibly, keeps its axis nearly straight, and, as it grows, turns round upon its base so far as to become transverse to its funiculus, and adnate to its upper part for some distance. Therefore in this case the attachment of the funiculus or stalk is about the middle, the chalaza is at one end, the orifice at the other.

Anatropous or Inverted, as in Fig. 347, the commonest kind, so called because in its growth it has as it were turned over upon its stalk, to which it has continued adnate. The organic base, or chalaza, thus becomes the apparent summit, and the orifice is at the base, by the side of the hilum or place of attachment. The adnate portion of the funiculus, which appears as a ridge or cord extending from the hilum to the chalaza, and which distinguishes this kind of ovule, is called the RHAPHE. The amphitropous ovule (Fig. 346) has a short or incomplete rhaphe.

322. Fig. 348-352 show the stages through which an ovule becomes anatropous in the course of its growth. The annexed two figures are sections of such an ovule at maturity; and Fig. 355 is Fig. 353 enlarged, with the parts lettered.