[301.] The Pistil, when only one, occupies the centre of the flower; when there are two pistils, they stand facing each other in the centre of the flower; when several, they commonly form a ring or circle; and when very numerous, they are generally crowded in rows or spirals on the surface of a more or less enlarged or elongated receptacle. Their number gives rise to certain terms, the counterpart of those used for stamens ([284]), which are survivals of the names of orders in the Linnæan artificial system. The names were coined by prefixing Greek numerals to -gynia used for gynœcium, and changed into adjectives in the form of -gynous. That is, a flower is
Monogynous, when it has a single pistil, whether that be simple or compound;
Digynous, when it has only two pistils; Trigynous, when with three; Tetragynous, with four; Pentagynous, with five; Hexagynous, with six; and so on to Polygynous, with many pistils.
[302.] The Parts of a Complete Pistil, as already twice explained ([16], [236]), are the Ovary, the Style, and the Stigma. The ovary is one essential part: it contains the rudiments of seeds, called Ovules. The stigma at the summit is also essential: it receives the pollen, which fertilizes the ovules in order that they may become seeds. But the style, commonly a tapering or slender column borne on the summit of the ovary, and bearing the stigma on its apex or its side, is no more necessary to a pistil than the filament is to the stamen. Accordingly, there is no style in many pistils: in these the stigma is sessile, that is, rests directly on the ovary (as in Fig. [326]). The stigma is very various in shape and appearance, being sometimes a little knob (as in the Cherry, Fig. [271]), sometimes a point or small surface of bare tissue (as in Fig. [327-330]), and sometimes a longitudinal crest or line (as in Fig. [324], [341-343]), or it may occupy the whole length of the style, as in Fig. [331].
303. The word Pistil (Latin, Pistillum) means a pestle. It came into use in the first place for such flowers as those of Crown Imperial, or Lily, in which the pistil in the centre was likened to the pestle, and the perianth around it to the mortar, of the apothecary.
304. A pistil is either simple or compound. It is simple when it answers to a single flower-leaf, compound when it answers to two or three, or a fuller circle of such leaves conjoined.
[305.] Carpels. It is convenient to have a name for each flower-leaf of the gynœcium; so it is called a Carpel, in Latin Carpellum or Carpidium. A simple pistil is a carpel. Each component flower-leaf of a compound pistil is likewise a carpel. When a flower has two or more pistils, these of course are simple pistils, that is, separate carpels or pistil-leaves. There may be only a single simple pistil to the flower, as in a Pea or Cherry blossom (Fig. [271]); there may be two such, as in many Saxifrages; or many, as in the Strawberry. More commonly the single pistil in the centre of a blossom is a compound one. Then there is seldom much difficulty in ascertaining the number of carpels or pistil-leaves that compose it.
[306.] The Simple Pistil, viewed morphologically, answers to a leaf-blade with margins incurved and united where they meet, so forming a closed case or pod (the ovary), and bearing ovules at the suture or junction of these margins: a tapering upper portion with margins similarly inrolled, is supposed to form the style; and these same margins, exposed at the tip or for a portion of the length, become the stigma. Compare, under this view, the three accompanying figures.