genus descriptions: SSTAs

Terrestrial herbs with fleshy or tuberous roots and leafy, unbranched stems. Flowers resupinate, usually yellow, orange or greenish, rarely white, often in short, dense heads. Sepals free, dorsal sepal forming a hood with petals. Lip entire or 3-lobed, spurred. Column erect; anther erect with parallel locules, canals adnate to side lobes of rostellum. Rostellum large, usually placed in front of anther which is often overtopped by mid-lobe; lateral lobes porrect, usually projecting beyond hood but sometimes short and shoulder-like. Stigmatic processes thickened with rounded ends.

Annual or perennial herbs; stem short or elongate. Leaves spirally arranged, narrow, thin to thick and coriaceous. Capitula single or in umbels, villous; floral bracts present; flowers 2- or 3-merous; petals eglandular. Male flowers: sepals free except at extreme base; petals connate into a glabrous infundibular tube bearing stamens on its truncate upper margin; petal tube finally involute and enclosing stamens; rudimentary pistil present; stamens as many as petals, white. Female flowers: sepals free except at extreme base, and usually becoming rigid at maturity; petals free; style with simple or bifid glandular appendages alternating with stigmas. Seeds variable, often with longitudinal ridges.

Submerged, dioecious marine perennial herbs; roots unbranched; horizontal scale-bearing rhizomatous axes (long shoots) buried in substrate giving rise, at regular intervals, to erect, contracted, leaf-bearing axes (short shoots). Leaves distichous, 2

Submerged, freshwater annual or perennial herbs, gynodioecious; roots unbranched; stems horizontal and stoloniferous below, erect and spreading above; bulbil-like turions (hibernacula) developing underground terminally on stolons, or axillary on erect stems or their branches. Leaves opposite and scale-like towards base of stem or branch, otherwise linear to ovate and in whorls of 3