Including DecaisneaceaeExcluding Sargentodoxaceae
Habit and leaf form. Lianas (with striate branches), or shrubs (Decaisnea). Self supporting, or climbing (mostly); when climbing, stem twiners; Akebia, Stauntonia twining anticlockwise. Leaves alternate; petiolate; non-sheathing; compound; pulvinate; ternate, or pinnate (only in Decaisnea), or palmate. Leaflets pulvinate. Lamina pinnately veined, or palmately veined (usually); cross-venulate. Leaves usually exstipulate.
General anatomy. Plants with laticifers (Decaisnea), or without laticifers. The laticifers of Decaisnea, only in the fruits.
Leaf anatomy. Stomata present; anomocytic.
The mesophyll containing calcium oxalate crystals. The mesophyll crystals druses (rarely), or solitary-prismatic (usually). Minor leaf veins without phloem transfer cells (Holboellia).
Stem anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar. Primary vascular tissue comprising a ring of bundles. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Xylem without tracheids; with fibre tracheids, or without fibre tracheids; with libriform fibres; with vessels. Vessel end-walls simple (usually), or scalariform (Decaisnea). Wood partially storied (VP, VPI); parenchyma very sparse or absent. Sieve-tube plastids S-type.
Reproductive type, pollination. Unisexual flowers present. Plants monoecious, or dioecious, or polygamomonoecious (Decaisnea only). Female flowers with staminodes (six, small), or without staminodes. Gynoecium of male flowers pistillodial to absent. Floral nectaries present, or absent. Nectar secretion from the perianth, or from the androecium (from the ‘honey-leaves’, when these present).
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes (these often drooping). The ultimate inflorescence unit racemose. Inflorescences axillary; solitary or fascicled racemes, often drooping, originating from scaly axillary buds. Flowers bracteolate, or ebracteolate; small; often fragrant; regular; 3 merous; cyclic (commonly P3+3, A3+3, G3 or more). Free hypanthium absent.
Perianth with distinct calyx and corolla, or sepaline; 3, or 6, or 9–12, or 12–50; isomerous. Calyx 3 (Akebia), or 6 (usually, rarely ‘many’, commonly petaloid, but small); 1 whorled (Akebia), or 2 whorled (mostly, rarely more?); polysepalous; regular; imbricate, or imbricate and valvate (the outer members sometimes valvate). Corolla when present, 6 (smaller than the sepals, in the form of nectariferous ‘honey-leaves’ between P and A — cf. Ranunculaceae); 2 whorled; polypetalous; regular.
Androecium 6. Androecial members free of the perianth; free of one another (Akebia, Holboellia), or coherent (usually, via connate filaments); when joined, 1 adelphous. Androecium of male flowers exclusively of fertile stamens. Stamens 6; alternisepalous (opposite the petals, when these present); opposite the corolla members (when C present); laminar (the sacs often more or less embedded in a laminar-thickened connective), or filantherous. Anthers adnate (or embedded); dehiscing via longitudinal slits; extrorse (or the thecae tilted upwards in Sinofranchetia); tetrasporangiate; appendaged (usually apiculate, by terminal prolongation of the connective), or unappendaged (muticous in Akebia). Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. The initial microspore tetrads tetrahedral, or decussate. Anther wall initially with more than one middle layer. Tapetum glandular. Pollen grains aperturate; (2–)3 aperturate; colpate, or colporate (col(por)oidate); 2-celled.
Gynoecium 3 carpelled, or 6–15 carpelled; apocarpous; eu-apocarpous (the divergent carpels in 1–5 whorls of three); superior. Carpel fully closed, or incompletely closed (e.g.in Akebia); more or less non-stylate (the stigma sessile or subsessile); apically stigmatic; (4–)10–100 ovuled (usually ‘numerous’). Placentation marginal (the ovules biseriate along the ventral suture, in Decaisnea), or dispersed (usually, the ovules inserted all over the carpel wall in separate alveolae). Stigmas wet type; non-papillate. Ovules orthotropous to anatropous; 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 (Holboellia), or persistent. Synergids pear-shaped. Endosperm formation cellular.
Fruit fleshy; an aggregate. The fruiting carpel dehiscent, or indehiscent; a follicle (fleshy), or baccate. Seeds endospermic. Endosperm oily. Embryo well differentiated (small). Cotyledons 2; flat. Embryo straight.
Seedling. Germination phanerocotylar.
Physiology, biochemistry. Not cyanogenic. Alkaloids absent (one species). Iridoids not detected. Proanthocyanidins present, or absent; cyanidin (Holboellia). Flavonols present; kaempferol and quercetin. Ellagic acid absent (3 species, 2 genera). Arbutin absent. Saponins/sapogenins commonly present. Aluminium accumulation not found. Sugars transported as sugar alcohols + oligosaccharides + sucrose (Holboellia).
Geography, cytology. Holarctic, Paleotropical, and Neotropical. Temperate to sub-tropical. Himalayas to Japan, Chile. 2n = 28, 30, 32.
Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Ranunculiflorae; Ranunculales. Cronquist’s Subclass Magnoliidae; Ranunculales. APG 3 core angiosperms; peripheral eudicot; Superorder Ranunculanae; Order Ranunculales.
Species 35. Genera 8; Akebia, Boquila, Decaisnea, Holboellia, Lardizabala, Parvatia, Sinofranchetia, Stauntonia.
Economic uses, etc. The fleshy follicles of Akebia spp. are edible.
• Technical details: Decaisnea, Holboellia, Lardizabala.
• Technical details: Akebia (Goebel).