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The families of flowering plants.                                                                                                                                                                

Nitrariaceae Bercht & J. Presl

                        

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ExcludingPeganiaceae, Tetradiclidaceae

Habit and leaf form. Shrubs (sometimes spiny). Plants succulent. Xerophytic (in salt deserts). Leaves deciduous; alternate; spiral (or fasciculate); fleshy; petiolate, or subsessile; non-sheathing; simple; epulvinate. Lamina dissected (apically trifid), or entire; if dissected, palmatifid; one-veined, or palmately veined. Leaves stipulate. Stipules intrapetiolar; free of one another; small; caducous (often), or persistent.

Leaf anatomy. Mucilaginous epidermis absent (?). Stomata present; anomocytic (mainly), or paracytic, or actinocytic. Hairs present; eglandular; unicellular. Unicellular hairs unbranched. Complex hairs absent.

Lamina dorsiventral, or isobilateral (?), or centric. The mesophyll containing mucilage cells; with sclerencymatous idioblasts, or without sclerenchymatous idioblasts (?); containing calcium oxalate crystals. The mesophyll crystals druses and solitary-prismatic.

Stem anatomy. Secretory cavities present; with mucilage. Primary vascular tissue in a cylinder, without separate bundles. Secondary thickening developing from a conventional cambial ring, or anomalous (?). ‘Included’ phloem absent. Xylem without fibre tracheids; with libriform fibres. Vessel end-walls horizontal to oblique; simple. Wood parenchyma paratracheal.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes (scorpioid). The ultimate inflorescence unit cymose. Inflorescences once or twice forked scorpioid cymes.Flowers bracteate (the bracts caducous); ebracteolate; small (less than 1 cm long); regular; more or less 5 merous; cyclic; polycyclic. Free hypanthium present.

Perianthwith distinct calyx and corolla; 10; 2 whorled; isomerous. Calyx 5; 1 whorled; polysepalous (?), or gamosepalous (‘connate below’); regular; fleshy; persistent; non-accrescent; imbricate. Corolla 5; 1 whorled; polypetalous (the petals concave, with inflexed apices); (induplicate-) valvate; regular; white.

Androecium (10–)15. Androecial members free of the perianth (on the hypanthium); free of one another; 3 whorled (?). Stamens (10–)15 (usually three times the number of petals); triplostemonous; both alternating with and opposite the corolla members. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; introrse; tetrasporangiate. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. Anther wall of the ‘dicot’ type. Pollen grains aperturate.

Gynoecium 2–6 carpelled. Carpels reduced in number relative to the perianth, or isomerous with the perianth, or increased in number relative to the perianth. The pistil 2–6 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 2–6 locular; sessile. Gynoecium stylate. Styles 1; attenuate from the ovary; apical. Stigmas or stigmatic lines as many as the locules. Placentation axile to apical. Ovules differentiated; 1 per locule; long funicled; pendulous; apotropous; with ventral raphe; non-arillate; anatropous; bitegmic; crassinucellate. Embryo-sac development Polygonum-type. Endosperm formation nuclear. Embryogeny solanad.

Fruit fleshy; indehiscent; a drupe (often edible, purple, red or yellow). The drupes with one stone (by abortion). Fruit 1 seeded. Seeds non-endospermic. Cotyledons 2. Embryo chlorophyllous; straight (the radicle next to the hilum).

Seedling.Germination phanerocotylar.

Physiology, biochemistry. Mustard-oils present, or absent (not specified, in descriptions seen, though it would seem important to know). Not cyanogenic. Iridoids not detected. Proanthocyanidins absent. Flavonols present. Aluminium accumulation not found. C3. C3 physiology recorded directly in Nitraria. Anatomy non-C4 type.

Geography, cytology. Holarctic, Paleotropical, and Australian. Sahara and southern Russia to Afghanistan and E. Siberia, one in southern Australia.

Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae; Sapindales (re-assigned). Cronquist’s Subclass Rosidae; Sapindales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; malvid; Order Sapindales.

Species 9. Genera 1; Nitraria.

General remarks. Sheahan and Chase (1996) recommended recognising this family as belonging to the order Sapindales, and not closely related to Zygophyllaceae s. str. (q.v.). The data on anther development, pollen structure and embryology are here riskily extrapolated from those for Zygophyllaceae sensu lato.

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