Aristolochia
Description
Aromatic woody or herbaceous vines, roots often tuberous; stem of several species with thick, fissured cork. Leaves: with or without axillar pseudostipules; petioles long, twisting; blades entire, 3-lobed in 2 species, base usually cordate, venation prominent beneath, main veins pedate at base, tertiary veins forming a tight net. Flowers solitary or in racemose or cymose inflorescences, axillary or cauliflorous; flowers resupinate, as a result of twisting of the inferior ovary; perianth composed of 3 sepals, zygomorphic, slightly curved to tightly S-shaped, its 3 parts easy to distinguish: the basal, inflated utricle, the narrow or trumpet-shaped median tube, the distal part, usually 1- to 3-lobed, very variable in shape, size and colour; ovary 6-celled, long and narrow, barely thicker than the pedicel, apex forming a hexandrous gynostemium with 6 anthers and 6 stigmatic lobes in the utricle. Capsules 6-locular, cylindric, with dorsal keel on each cell; dehiscence septicidal, starting from the peduncle and incomplete, dehisced fruit basket-like; seeds numerous, generally flat, piled in each cell, often winged, seed coat slightly verrucose, adaxially with a longitudinal prominent raphe.
Distribution
Guianas present, Tropical and subtropical regions of the world present
Tropical and subtropical regions of the world; only a few temperate species. In the Guianas in dense primary forest and secondary vegetation or disturbed areas.
Phenology
Flowering is erratic among the species growing in the forest in the Guianas. All species are rarely collected (which does not permit to draw trustable conclusions about the phenology of the taxa growing in open vegetation).
Uses
Several species are in cultivation in tropical and temperate areas as greenhouse or garden plants prized for their flowers. Often Aristolochia species are used in folk medicine.
Taxonomy
All known South American species belong to sect. Gymnolobus Duchartre subsect. Hexandrae Duchartre as traditionally accepted since Duchartre (1864). Gonzalez (1991) divided this subsect. in 2 series:
According to this system,A. consimilis Masters and A. paramaribensis Duchartre should fall into ser. Thyrsicae . As far as their fruits are known, the other Guianan species belong to ser. Hexandrae subser. Hexandrae (non cauliflorous) and subser. Anthocaulicae Gonzalez (cauliflorous).
According to this system,
Wood
Growth rings absent.
Vessels diffuse, solitary (up to 90%), and some irregular clusters of 2-3, round to slightly oval, the longest axis is in tangential direction, 16-19(8-25) per sq. mm, diameter variable, in two distinct size groups, 50-55(35-85) and 150-190(115-210) pm, respectively. Vessel-member length: 256(184-311) μm. Perforations simple. Intervascular pits scarce, alternate, round to oval, 4-7 μm. Vessel-ray and vessel-parenchyma pits similar to slightly larger than the intervascular pits. Thin-walled tyloses scarcely present.
Rays large, interfascicular, dissecting the stem into bundles with fibre tracheids, vessels and parenchyma; multiseriate, 10-20 cells wide, 1(0-2) per mm, up to >9000 μm (= >220 cells) high. Heterogeneous, composed of various shapes of procumbent cells and few square/upright cells. Rhombic crystals abundant.
Parenchyma few, scanty paratracheal and some diffuse strands.
Fibre tracheids, thin-walled, lumen up to 12-18 pm, walls up to 3-4 μm. Pits clearly bordered, abundant on radial and tangential walls, 4-6 μm. Length: 914(690-1208) μm. FN ratio: 3.57.