Fig. 349.—Humulus lupulus: fruit in longitudinal section.
Figs. 350–353.—Cannabis sativa: 350, ♂-plant; 351, ♂-flower; 352, ♀-flower, entire and in longitudinal section; 353, fruit in longitudinal section.
Family 6. Polygonifloræ.
This family is on one side closely allied to the Urticaceæ by its solitary, basal, vertical, and straight ovule, and by the conical ocrea which envelopes the younger leaves in the bud, similar characters being present in the Urticaceæ. On the other side it is related to the Curvembryæ. The flowers are small, often trimerous, regular and slightly perigynous (in Chloranthaceæ, if they properly belong to this family, and Houttuynia, more or less epigynous). Syncarps are present in some Piperaceæ, but the fruit is generally a single fruit, one-seeded berry, nut or drupe. The leaves are generally scattered.
Order 1. Polygonaceæ. The majority are herbaceous plants with round, often jointed stems, scattered leaves and ocrea, that is a membranous, tubular, ligular or stipular structure inside the base of the leaf, which clasps the stem and axillary bud; the edges of the lamina are rolled backwards in the bud. The flowers are regular, small, generally ☿, slightly perigynous, with inconspicuous, simple, green or white perianth of 5–6 free segments; stamens 5–9 (Fig. [354]) sometimes arranged in two series; gynœceum 2–3 carpels, ovary unilocular with one basal, straight (orthotropous) ovule, 2–3 free styles. The fruit is a 2–3-angular nut; the embryo, with mealy endosperm, is straight or curved (Fig. [355] H), often unsymmetrical.—The inflorescences are compound, and generally branch from the axils of the bracteoles, so that the last partial-inflorescences become coiled, uniparous scorpioid cymes; in Polygonum the two bracteoles unite into a membranous tube; in Rheum and Rumex there is only one bracteole.
