The Elements of Botany, For Beginners and For Schools

by Asa Gray

Fig. 326. Simple pistil of Podophyllum, cut across, showing ovules borne on placenta.

Fig. 327. Pistil of a Saxifrage, of two simple carpels or pistil-leaves, united at the base only, cut across both above and below.

Fig. 328. Compound 3-carpellary pistil of common St. John's-wort, cut across: the three styles separate.

Fig. 329. The same of shrubby St. John's-wort; the three styles as well as ovaries here united into one.

Fig. 330. Compound 3-carpellary pistil of Tradescantia or Spiderwort; the three stigmas as well as styles and ovary completely coalescent into one.

[309.] A Compound Pistil is a combination of two, three, or a greater number of pistil-leaves or carpels in a circle, united into one body, at least by their ovaries. The annexed figures should make it clear. A series of Saxifrages might be selected the gynœcium of which would show every gradation between two simple pistils, or separate carpels, and their complete coalescence into one compound and two-celled ovary. Even when the constituent styles and stigmas are completely coalescent into one, the nature of the combination is usually revealed by some external lines or grooves, or (as in Fig. [328-330]) by the internal partitions, or the number of the placentæ. The simplest case of compound pistil is that

[310.] With two or more Cells and Axile Placentæ, namely, with as many cells as there are carpels, that have united to compose the organ. Such a pistil is just what would be formed if the simple pistils (two, three, or five in a circle, as the case may be), like those of a Pæony or Stonecrop (Fig. [224, 225]), pressed together in the centre of the flower, were to cohere by their contiguous parts. In such a case the placentæ are naturally axile, or all brought together in the axis or centre; and the ovary has as many Dissepiments, or internal Partitions, as there are carpels in its composition. For these are the contiguous and coalescent walls or sides of the component carpels. When such pistils ripen into pods, they often separate along these lines into their elementary carpels.