Family Aristolochiaceae
General anatomy. Plants with silica bodies, or without silica bodies. Leaf anatomy. Epidermis containing silica bodies, or without silica bodies. Stomata present; anomocytic. Lamina dorsiventral (usually), or isobilateral. The mesophyll with spherical etherial oil cells, or without etherial oil cells. Minor leaf veins without phloem transfer cells (Aristolochia, Asarum). Stem anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar. Primary vascular tissue comprising a ring of bundles. Secondary thickening developing from a conventional cambial ring (but sometimes the pith and primary medullary rays are unusually dilated, deforming the secondarily thickened structure). Xylem with fibre tracheids, or without fibre tracheids. Vessel end-walls simple. Primary medullary rays wide. Wood parenchyma apotracheal, or paratracheal. Sieve-tube plastids P-type; type I (a), or type II (a). Reproductive type, pollination. Plants hermaphrodite. Pollination entomophilous; via diptera; mechanism conspicuously specialized (via an elaborate system for trapping flies within the perianth tube, involving articulated hairs which subsequently wither to release them). Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, or in racemes, or in spikes. The ultimate inflorescence unit cymose, or racemose. Inflorescences terminal, or axillary; terminal or lateral racemes or cymes. Flowers small to large; often malodorous (smelling of carrion), or odourless (?); regular to very irregular; cyclic; tricyclic to pentacyclic. Perianth with distinct calyx and corolla, or petaline; 3, or 6; joined; 1 whorled, or 2 whorled (the corolla whorl conspicuous and well developed only in Saruma); when two-whorled, isomerous. Calyx 3; 1 whorled; gamosepalous; entire, or blunt-lobed; campanulate, or tubular (the tube often S-shaped); unequal but not bilabiate, or bilabiate, or regular; persistent, or not persistent; valvate (or valvate-induplicate). Corolla when present, 3 (usually reduced or absent); 1 whorled. Androecium 6–36. Androecial members free of the perianth; united with the gynoecium (forming a gynostemium by fusion to the style of the filaments, or of both the filaments and the anthers), or free of the gynoecium; free of one another, or coherent (via the gynostemium); when joined, 1 adelphous; 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens. Stamens 4, or 6 (commonly), or 12(–36); isomerous with the perianth to polystemonous; filantherous, or with sessile anthers. Anthers cohering, or separate from one another; basifixed, or adnate; non-versatile; dehiscing via longitudinal slits; extrorse, or extrorse and introrse (Heterotropa); tetrasporangiate; appendaged (apically, with the expanded connective assuming stigmatic functions in association with the gynostemium), or unappendaged. Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis successive, or simultaneous. The initial microspore tetrads tetrahedral, or isobilateral, or decussate, or T-shaped (rarely). Anther wall initially with more than one middle layer; of the ‘dicot’ type. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate, or nonaperturate; 1–7 aperturate; sulcate, or sulculate (monosulcate to multisulcoidate or sulculate); 2-celled. Gynoecium 4–6 carpelled. Carpels isomerous with the perianth to increased in number relative to the perianth. The pistil 1 celled, or 4–6 celled. Gynoecium syncarpous; synovarious (Hexastylis), or synstylovarious, or eu-syncarpous; partly inferior (sometimes), or inferior (usually). Ovary 4–6 locular, or 1 locular (the septa sometimes incompletely intruded). Epigynous disk present, or absent. Gynoecium stylate. Styles 1, or 4–6; free, or partially joined; apical. Stigmas dry type (mostly), or wet type (?); papillate; Group II type, or Group III type (?). Placentation when unilocular, parietal; when plurilocular, axile. Ovules in the single cavity when unilocular, 50–100 (‘many’); when plurilocular, 20–50 per locule (‘many’); funicled; pendulous, or horizontal; anatropous (or circinotropous); bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral, or persistent. Synergids pear-shaped. Hypostase present. Endosperm formation cellular. Embryogeny probably solanad. Fruit non-fleshy (usually), or fleshy (sometimes with a fleshy endocarp); dehiscent (usually), or indehiscent (rarely), or a schizocarp (Saruma). Mericarps in Saruma, 4–6 (?); in Saruma, comprising follicles. Fruit a capsule (usually), or a berry, or a nut. Capsules when dehiscent, septicidal and valvular (usually basally, rarely at the top), or splitting irregularly. Seeds endospermic. Endosperm ruminate, or not ruminate; oily. Embryo rudimentary at the time of seed release to weakly differentiated. Embryo achlorophyllous (2/3). Seedling. Germination phanerocotylar, or cryptocotylar. Physiology, biochemistry. Not cyanogenic. Alkaloids present (usually), or absent. Iridoids not detected. Proanthocyanidins absent. Flavonols present; quercetin, or kaempferol and quercetin. Ellagic acid absent (2 genera, 5 species). Arbutin absent. Aluminium accumulation not found. Inulin recorded (Aristolochia, Gibbs 1974). Geography, cytology. Temperate (warm), or sub-tropical to tropical. Widespread, except Australasia. X = 4–7, 12, 13. Supposed basic chromosome number of family: 7. Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Magnoliiflorae; Aristolochiales. Cronquist’s Subclass Magnoliidae; Aristolochiales. APG (1998) basal order. APG 3 (2009) Order: Piperales. Species 400. Genera 7; Apama, Aristolochia, Asarum, Euglypha, Holostylis, Saruma, Thottea. Economic uses, etc. A few Aristolochia and Asarum spp. cultivated as ornamentals. |
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