§ 11. The Pistil.
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120. The carpels (91) of the Pistil, although they may occasionally assume, rather more than stamens, the appearance and colour of leaves, are still more different in shape and structure. They are usually sessile; if stalked their stalk is called a podocarp. This stalk, upon which each separate carpel is supported above the receptacle, must not be confounded with the gynobasis (143), upon which the whole pistil is sometimes raised.
121. Each carpel consists of three parts
(1) the Ovary, or enlarged base, which includes one or more cavities of cells containing one or more small bodies called ovules. These are the earliest condition of the future seeds.
(2) the Style, proceeding from the summit of the ovary, and supporting -
(3) the Stigma, which is sometimes a point (or punctiform stigma) or small head (a capitate stigma) at the top of the style or ovary, sometimes a portion of its surface more or less lateral and variously shaped, distinguished by a looser texture, and covered with minute protuberance called papillæ.
122. The style is often wanting, and the stigma is the sessile on the ovary, but in the perfect pistil there is always at least one ovule in the ovary, and some portion of stigmatic surface. Without these the pistil is imperfect, and said to be barren (not setting seed), abortive, or rudimentary (84), according to the degree of imperfection.
123. The ovary being the essential part of the pistil most of the terms relating to the number, arrangement, etc., of the carpels apply specially to their ovaries. In some works each separate carpel is called a pistil, all those of a flower constituting together the gynÅcium; but this term is in little use, and the word pistil is more generally applied in a collective sense. When the ovaries are at all united, they are commonly termed a compound ovary.
124. The number of carpels or ovaries in a flower is frequently reduced below that of the parts of the other floral whorls, even in flowers otherwise symmetrical. In a very few genera, however the ovaries are more numerous than the petals, or indefinite. They are in that case either arranged in a single whorl, or form a head or spike in the centre of the flower.
125. The terms monogynous, digynous, polygynous, etc. (with a pistil of one, two, or more parts), are vaguely used, applying sometimes to the whole pistil, sometimes to the ovaries alone, or to the styles and stigmas only. When a more precise nomenclature is adopted, the flower is
monocarpellary, when the pistil consists of a single simple carpel.
bi-, tri-, etc., to poly-carpellary, when the pistil consists of two, three or an indefinite number of carpels, whether separate or united.
syncarpous, when the carpels or their ovaries are more or less united into one compound ovary.
apocarpous, when the carpels or ovaries are all free and distinct.
126. A compound ovary is
unilocular or one-celled, when there are no partitions between the ovules, or when those partitions do not meet in the centre so as to divide the cavity into several cells.
plurilocular or several-celled, when completely divided into two or more cells by partitions called disseptiments (septa), usually vertical and radiating from the centre or axis of the ovary to its circumference.
bi-, tri-, etc., to multi-locular, according to the number of these cells, two, three, etc., or many.
127. In general the number of cells or of dissepiments, complete or partial, or of rows of ovules, corresponds with that of the carpels, of which the pistil is composed. But sometimes each carpel is divided completely or partially into two cells, or has two rows of ovules, so that the number of carpels appears double what it really is. Sometimes again the carpels are so completely combined and reduced as to form a single cell, with a single ovule, although it really consists of several carpels. But in these case is usually described as it appears,a s well as such as it is theoretically supposed to be.
128. In apocarpous pistils the styles are usually free, each bearing its own stigma. Very rarely the greater part of the styles, or the stigmas alone, are united, whilst the ovaries remain distinct.
129. Syncarpous pistils are said to have
several styles, when the styles are free from the base.
one style, with several branches, when the styles are connected at the base, but separate below the point where the stigmas or stigmatic surfaces commence.
one simple style, with several stigmas, when united up to the point where the stigmas or stigmatic surfaces commence, and then separating.
one simple style, with a branched, lobed, toothed, notched, or entire stigma (as the case, may be), when the stigmas are more or less united. In many works, however, this precise nomenclature is not strictly adhered to, and considerably confusion is often the result.
130. In general the number of styles, or branches of the styles or stigma, is the same as that of the carpels, but sometimes that number is doubled, especially in the stigmas, and sometimes the stigmas are dichotomously or pinnately branched, or penicillate, that is, divided into a tuft of hair-like branches. All these variations sometimes make it a difficult task to determine the number of carpels forming a compound ovary, but the point is of considerable importance in fixing the affinities of plants, and, by careful consideration, the real as well as the apparent number has now in most cases been agreed upon.
131. The Placenta is the part of the inside of the ovary to which the ovules are, sometimes a mere point or line on the inner surface, often more or less thickened or raised. Placentation is therefore the indication of the part of the ovary to which the ovules are attached.
132. Placentas are
axile, when the ovaries are attached to the axis or centre, that is, in plurilocular ovaries, when the they are attached to the inner angle of each cell; in unilocular simple ovaries, which have almost always and excentrical style or stigma, when the ovules are attached to the side of the ovary nearest to the style; in unilocular compound ovaries, where the ovules are attached to a central protuberance, column of axis rising up from the base of the cavity. If this column does not reach the top of the cavity, the placenta is said to be free and central.
parietal, when the ovules are attached to the inner surface of the cavity of a one-celled compound ovary. Parietal ovaries are usually slightly thickened or raised lines, sometimes broad surfaces nearly covering the inner surface of the cavity, sometimes projecting far into the cavity, and constituting partial dissepiments, or even meeting in the centre, but without cohering there. In the latter case the distinction between the one-celled and several-celled ovary sometimes almost disappears.
133. Each Ovule (121), when fully formed, usually consists of a central mass or nucleus enclosed in two bag-like coats, the outer one called primine, the inner one secundine. The chalaza is the point of the ovule at which the base of the nucleus is confluent with the coats. The foramen is a minute aperture in the coats over the apex of the nucleus.
134. Ovules are
orthotropous or straight, when the chalaza coincides with the base (36) of the ovule, and the foramen is at the opposite extremity, the axis of the ovule being straight.
campylotropous or incurved, when the chalaza still coinciding with the base of the ovule, the axis of the ovule is curved, bringing the foramen down more or less towards that base.
anatropous or inverted, when the chalaza is at the apex of the ovule, and the foramen next to its base, the axis remaining straight. In this, one of the more frequent forms of the ovule, the chalaza is connected with the base by a cord, called rhaphe, adhering to one side of the ovule, and becoming more or less incorporated with its coats, as the ovule enlarges into a seed.
amphitropous or half-inverted, when the ovule being being as it were attached laterally the chalaza and foramen at opposite ends of its straight or curved axis are about equally distant from the base or point of attachment.
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