Family Scheuchzeriaceae
Scheuchzeriaceae RudolphiIncluding Borboraceae Dulac (p.p.) Habit and leaf form. Slender herbs. Perennial; with neither basal nor terminal aggregations of leaves (the leaves both cauline and basal); rhizomatous. Helophytic (in Sphagnum bogs). Leaves alternate; (semi) terete; sessile; sheathing. Leaf sheaths with free margins. Leaves simple. Lamina entire; acicular to linear (semi-terete, with a pore at the tip); parallel-veined. Axillary scales present (cf. Potamogetonaceae, sometimes expressed as hairs). General anatomy. Accumulated starch exclusively ‘pteridophyte type’. Leaf anatomy. Stomata present; tetracytic. The mesophyll containing calcium oxalate crystals. The mesophyll crystals druses (?), or solitary-prismatic (? — no raphides). Vessels absent. Stem anatomy. Secondary thickening absent. Xylem without vessels. Root anatomy. Root xylem with vessels; vessel end-walls scalariform. Reproductive type, pollination. Unisexual flowers absent. Plants hermaphrodite. Pollination anemophilous (protogynous). Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes. The ultimate inflorescence unit racemose. Inflorescences terminal; terminal, bracteate racemes. Flowers bracteate; regular; 3 merous; cyclic; pentacyclic. Perigone tube absent. Perianth of ‘tepals’; 6; free; 2 whorled (3+3); isomerous; sepaloid to petaloid; green, or cream. Androecium 6. Androecial members free of the perianth; free of one another; 2 whorled (3+3). Androecium exclusively of fertile stamens. Stamens 6; diplostemonous; alterniperianthial; filantherous (the filaments short). Anthers basifixed (elongate); non-versatile; dehiscing via longitudinal slits; extrorse; tetrasporangiate. Tapetum amoeboid. Pollen shed in aggregates; in diads. Pollen grains nonaperturate; 3-celled. Gynoecium 3 carpelled, or 6 carpelled. Carpels isomerous with the perianth, or increased in number relative to the perianth. The pistil basally 3 celled, or 6 celled. Gynoecium apocarpous to syncarpous; semicarpous (the carpels slightly connate at the base, otherwise distinct); superior. Carpel incompletely closed (‘extrorse’ at the tip); 2(–5) ovuled. Placentation marginal to basal. Ovary basally 3 locular, or 6 locular. Stigmas dry type; papillate; Group II type. Ovules ascending; anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells not formed (the three nuclei soon degenerating). Synergids pear-shaped. Endosperm formation helobial. Endosperm haustoria absent. Embryogeny probably caryophyllad. Fruit non-fleshy; an aggregate (or more or less schizocarpic). The fruiting carpel dehiscent; viewed as semicarpous, a follicle (the follicles recurved-spreading). Fruit perhaps viewable as a schizocarp. Mericarps if regarded as schizocarpic, 3, or 6; comprising follicles. Seeds non-endospermic. Seeds with starch. Embryo well differentiated. Cotyledons 1. Embryo chlorophyllous (Scheuchzeria palustris). Seedling. Germination phanerocotylar. Hypocotyl internode absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated to compact (short, but swollen for storage); more or less circular in t.s. Coleoptile absent. Seedling non-macropodous. First leaf dorsiventral. Primary root ephemeral. Physiology, biochemistry. Cyanogenic. Cynogenic constituents tyrosine-derived (triglochinin). Alkaloids absent. Proanthocyanidins present. Saponins/sapogenins absent. Geography, cytology. Holarctic. Frigid zone, or temperate (cool). Widespread in the cool North temperate and frigid zone. N = 11. Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Alismatiflorae; Zosterales. APG 3 core angiosperms; Superorder Lilianae; non-commelinid Monocot; Order Alismatales. Species 2. Genera 1; only genus, Scheuchzeria. Illustrations. |
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