The families of flowering plants.
Habit and leaf form. Shrubs, or ‘arborescent’, or herbs. Plants partially parasitic. When herbaceous, perennial. Leaves alternate; non-sheathing; ostensibly usually simple, or compound (overtly so in K. cystoides, perhaps basically so in the rest); unifoliolate (usually, rather than ‘simple’?), or ternate (K. cystoides). Lamina entire; cross-venulate. Leaves exstipulate. Lamina margins entire.
Leaf anatomy. Stomata present; paracytic, or anomocytic and paracytic.
The mesophyll with sclerencymatous idioblasts; containing calcium oxalate crystals. The mesophyll crystals druses.
Stem anatomy. Cork cambium present; initially deep-seated. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Vessel end-walls simple. Wood parenchyma scanty paratracheal.
Reproductive type, pollination. Plants hermaphrodite. Pollination entomophilous; via hymenoptera (oil-collecting bees).
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when solitary, axillary; when aggregated, in racemes; bi- bracteolate (the bracteoles leafy); minute; very irregular; zygomorphic. The floral irregularity involving the perianth and involving the androecium. Flowers cyclic; tetracyclic. Free hypanthium absent. Hypogynous disk absent.
Perianth with distinct calyx and corolla; (8–)10; 2 whorled; isomerous to anisomerous; all petaloid (including the calyx). Calyx (4–)5; 1 whorled; polysepalous; petaloid, unequal but not bilabiate (commonly with the three outer members larger than the two inner and often nearly enclosing the rest of the flower, rarely all the members reflexed); imbricate; with the median member anterior. Corolla (4–)5; 1 whorled; polypetalous, or partially gamopetalous (the three upper members sometimes connate via their claws); imbricate; unequal but not bilabiate (the two lower, abaxial members smaller, very different, commonly broad and thick, and often modified into lipid-secreting glands). Petals clawed (the three adaxial members), or sessile (the abaxial members).
Androecium (3–)4(–5). Androecial members adnate (sometimes adnate to the claws of the upper petals), or free of the perianth; markedly unequal (declinate); free of one another, or coherent; when joined, 1 adelphous (the filaments basally connate); 1 whorled. Androecium exclusively of fertile stamens, or including staminodes (rarely). Staminodes when present, 1 (in the form of a fifth, sterile, anterior stamen); in the same series as the fertile stamens; representing the anterior median member. Fertile stamens representing the posterior-lateral pair and the anterior-lateral pair. Stamens (3–)4 (posterior); reduced in number relative to the adjacent perianth; oppositisepalous (alternating with the upper petals); alternating with the corolla members; filantherous (the filaments thick). Anthers apically dehiscing via pores, or dehiscing via short slits; tetrasporangiate. Pollen grains aperturate; 3(–4) aperturate; colporate (to ruporate).
Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled, or 2 celled. Gynoecium syncarpous (but pseudomonomerous); disguisedly eu-syncarpous (one carpel developing, the other vestigial); superior. Ovary 1(–2) locular. Gynoecium stylate. Styles 1; obliquely apical. Stigmas 1 (discoid or punctiform). Placentation apical. Ovules in the single cavity 2; pendulous; collateral; anatropous; bitegmic.
Fruit non-fleshy (dry); indehiscent; achene-like (usually covered with bristles or spines, these often retrorsely barbed); 1 seeded. Seeds non-endospermic. Embryo well differentiated. Cotyledons 2 (thick). Embryo straight.
Physiology, biochemistry. Iridoids not detected (S.R. Jensen, unpublished). Saponins/sapogenins absent. Aluminium accumulation not found.
Geography, cytology. Holarctic and Neotropical. Temperate to tropical. Warm Central America. X = 6.
Taxonomy.Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Rutiflorae (probably misplaced); Polygalales. Cronquist’s Subclass Rosidae; Polygalales. APG 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Zygophyllales.
Species 25. Genera 1; only genus, Krameria.
General remarks. Linked with Zygophyllaceae s. str. on rbcL sequence data by Chase et al. (1993) and Sheahan and Chase (1996).