Description

Key Characters:

Growth Form: Subshrubs or shrubs, perennial, rarely annual herbs or somewhat fleshy plants.

Stems: Stems cylindrical or quadrangular, erect or decumbent, sometimes creeping and irregularly branched forming dense mats.

Roots:

Leaves: Leaves simple. Opposite. Leaves linear, ovate, elliptic, rarely slightly succulent.

Flowers: Flowers in inflorescences axillary, 5-25 per flowering branch, 1-10-florous; bracts foliaceous; flowers sessile; hypanthium obovate. Flowers insect-pollinated, bisexual (perfect), often heterostylous. Calyx 4-6 lobed, lobes equal or subequal. Corolla infundibuliform or salverform, white, lilac or pink, external surface glabrous, internal surface with a ring of moniliform hairs near the base of the tube; nectariferous disk entire or 2-lobed. Stamens as many as and alternate with the corolla lobes, exerted, slightly shorter than the corolla lobes; anthers dithecal, opening by longitudinal slits. Pollen grains 11–20 zonocolporate, suboblate to oblatespheroidal, polar axis (P) 49.1–100.6 μm and equatorial diameter 56.4–120 μm, with ECA/P = 0.28–0.5, endoaperture forming an endocingulum, with two supratectal elements: conical spines 1–8 μm long. Ovary inferior, occasionally partly so, or very rarely superior, 2(-5)-carpellate, with as many cells, rarely 1-celled; ovules 1 to numerous per cell, placentation axile, basal, apical, or rarely parietal, anatropous to hemitropous, usually with a funicular obturator and a massive single ingegument; style 1 or as many as carpels, terminal, slender; stigmas lobed or capitate, dry or occasionally wet.

Fruit: Schizocarps subspherical or obovate; laterally compressed in H. angustifolium and H. vaginale; mericarps with 3–5 carinate dorsal face; smooth in H. domingense; ventral face with two depressions; one on each side of the midline; scarcely evident in H. angustifolium. Seeds plano-convex; oblong or obovate in outline; embryo apically curved; except in H. angustifolium and H. vaginale where the embryo is straight; with well-developed oily endosperm; or endosperm occasionally scanty or absent.

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