Family Peganaceae

Peganaceae Tiegh. ex Takht.

~ Nitrariaceae

Habit and leaf form. Glabrous or hairy herbs (with terete stems); non-laticiferous and without coloured juice. Perennial (branched); with neither basal nor terminal aggregations of leaves. Leaves alternate; spiral; ‘herbaceous’, or leathery, or fleshy (?); sessile; non-sheathing; simple; epulvinate. Lamina dissected, or entire; when dissected, more or less irregularly pinnatifid; pinnately veined. Leaves stipulate, or exstipulate (Malacocarpus?). Stipules intrapetiolar; free of one another; setaceous; caducous.

Leaf anatomy. Mucilaginous epidermis present, or absent. Stomata present; anomocytic. Hairs present; glandular; multicellular. Multicellular hairs unbranched. Complex hairs present; capitate.

Adaxial hypodermis present, or absent. Lamina dorsiventral, or isobilateral (?). The mesophyll not containing mucilage cells; without sclerenchymatous idioblasts (these also lacking in the stems); containing calcium oxalate crystals. The mesophyll crystals raphides, or druses, or solitary-prismatic.

Stem anatomy. Secretory cavities absent (or at least, no mucilage cavities). Primary vascular tissue in a cylinder, without separate bundles. Secondary thickening developing from a conventional cambial ring (?). Xylem without fibre tracheids; with libriform fibres. Vessel end-walls horizontal to oblique; simple.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’ (towards the ends of the stems); leaf-opposed. Inflorescences or one-flowered peduncles leaf-opposed. Flowers small to medium-sized; regular; 4–5 merous; polycyclic. Floral receptacle developing a gynophore, or with neither androphore nor gynophore (?). Hypogynous disk present; intrastaminal; annular.

Perianth with distinct calyx and corolla; 8, or 10; 2 whorled; isomerous. Calyx 4, or 5; 1 whorled; polysepalous (?); regular; non-fleshy; persistent (often leafy and pinnatifid); valvate. Corolla 4, or 5; 1 whorled; polypetalous; imbricate; more or less regular; white.

Androecium 12, or 15. Androecial members free of the perianth; free of one another; 3 whorled. Androecium exclusively of fertile stamens. Stamens 12, or 15; triplostemonous; both alternating with and opposite the corolla members; filantherous (the filaments dilated basally). Microsporogenesis simultaneous. Anther wall of the ‘dicot’ type. Tapetum glandular. Pollen grains aperturate.

Gynoecium 2–3 carpelled. Carpels reduced in number relative to the perianth. The pistil 2–3 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 2–3 locular; subsessile. Gynoecium stylate. Styles 1; from a depression at the top of the ovary; apical. Stigmas 1 (with 2–3 stigmatic ridges); dry type; papillate; Group II type. Placentation axile to apical. Ovules differentiated; 10–50 per locule (‘many’); funicled; pendulous; apotropous; with ventral raphe; non-arillate; anatropous (?); bitegmic; crassinucellate. Embryo-sac development Polygonum-type. Endosperm formation nuclear.

Fruit fleshy, or non-fleshy; dehiscent (Peganum), or indehiscent (Malacocarpus); a capsule, or a berry. Capsules of Peganum loculicidal. Fruit 10–100 seeded (‘many’). Seeds endospermic. Cotyledons 2. Embryo chlorophyllous; curved.

Seedling. Germination phanerocotylar.

Physiology, biochemistry. Mustard-oils present, or absent (not specified, in descriptions seen, though it would seem important to know). Alkaloids present. C3. C3 physiology recorded directly in Peganum. Anatomy non-C4 type.

Geography, cytology. Holarctic and Neotropical. Temperate and sub-tropical. Mediterranean to Mongolia, southern U.S. and Mexico.

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 (as a synonym of Nitrariaceae).

Species 5–7. Genera 2; Malacocarpus, Peganum.

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

Economic uses, etc. A dye (‘Turkey red’) from the seeds is used for dyeing hats (tarbooshes).