Xyridaceae

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Xyridaceae

Description

Rosulate or caulescent, fine to coarse terrestrial herbs, the roots mostly slender, diffuse-fibrous, with root hairs; axis sympodial or monopodial. Leaves alternate and equitant-distichous, or in spirals, ligulate or eligulate, the bases broad, open-sheathing, the blades laterally to dorsiventrally compressed, in either case linear. Inflorescences lateral to terminal, scapose, scapes 1 to few from the axil of scape sheaths or inner leaves, naked or with distant pairs of scape bracts, each scape bearing 1 (or more) imbricate-bracted spikes or heads, at apex rarely a panicle of spikes. Flowers perfect, 1 to many per spike or head, solitary and subsessile to shortly pedicellate in the axil of chaffy, coriaceous to scarious bracts; perianth of 2 differentiated whorls; sepals (2)3, the anterior (inner) one reduced or lacking, or equal to the others or, mostly, membranaceous and wrapped around the corolla bud, abscissing as the flower opens or persistent, the other 2 subopposite, connivent to variously connate, chaffy, mostly boat-shaped, often keeled, persisting around the ripe fruit; petals 3, equal or unequal, free and then clawed, or connate and fused into a tube, salverform or bilabiate, the spreading blades broad, yellow to white or blue; stamens 3, epipetalous; staminodes 0-3, scale-like to filamentous, bifid and bearded or beardless, or reduced; anthers mostly tetrasporangiate, usually bilocular at anthesis, introrsely or laterally dehiscing longitudinally; pollen monosulcate or inaperturate; ovary superior, tricarpellate, unilocular to completely or incompletely trilocular, the placentation thus marginal, parietal, basal, free-central or axile, ovules orthotropous to anatropous or weakly campylotropous, style 1, terminal, tubular, mostly elongate, 3-branched or simple to irregularly infundibular at apex, stigmas usually 3, each at the end of a style' branch or trilobed-confluent or as a rim of fimbriae. Fruit capsular, mostly loculicidal; seeds mostly numerous (-1), usually with strong longitudinal ridges and finer cross-lines, translucent or farinose-opaque, the embryo small, situated at base of an abundant mealy endosperm.

Distribution

Guayana Highlands: present present Guianas: present Southern America:, Paraguay (Paraguay present) pantropic: present
A largely pantropic family of 5 genera and ca. 300 spe- cies, with Xyris totalling around 200 species the only genus occurring in both hemispheres. Of the other genera Aratitiyopea Steyerm. & Berry (monospecific, 2 var.), Achlyphila Maguire & Wurdack (monospecific), and Orectanthe Maguire (2 species) are confined to the Guayana Highlands; Abolboda (ca. 20 species), while most diverse in the Guayana Highlands, extends southward through Brazil to Paraguay (one record); in the Guianas there are 34 species in 3 genera.