Hippocrateaceae

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Hippocrateaceae

Description

Lianas, shrubs or slender trees, usually glabrous. Branches usually opposite. Leaves opposite or subopposite (alternate in a few extra-Guianan species). Stipules inconspicuous, caducous. Petioles canaliculate; blades entire to crenate, irregularly distributed black dots often present at the lower surface, often minute glandular dots at the margin. Many species show a well developed latex-system. Inflorescences thyrsoid-paniculate, corymbose, pseudo-cymose, (pseudo-) dichotomously branched or fasciculate, often with yellow exudate in flowers, fruits and occasionally on the branches. Flowers bisexual; calyx not covering the petals in bud, sepals 5, equal or unequal, connate at the base, imbricate; petals 5, free, in bud imbricate (valvate in African species of Hippocratea), suberect or spreading at anthesis; disk extrastaminal, variable in shape: i.e. a low ring, short-tubular, saucer-like, cushion-like, with or without flattened margin, the latter may even be upturned, or disk forming staminiferous pockets; stamens 3 (5 in Cheiloclinium anomalum),
filaments ligulate, often considerably widened toward the base, often recurved, anthers basifixed, extrorsely or apically dehiscent by transverse or obliquely confluent clefts, or by vertical not confluent clefts (Peritassa); ovary superior, 3-locular (5-locular in Cheiloclinium anomalum), placentation axile, ovules 2-14 per locule, superposed or collateral, style present or absent, stigmas obsolete, or forming a terminal shield, or stigmas 3 (5 in Cheiloclinium anomalum), deltoid, entire or emarginate to conspicuously bilobed, opposite to or alternating with the stamens. Fruits either capsular or drupaceous; capsular fruits consisting of 3 mericarps attached to a receptacle, free or connate for the basal half, dehiscent along the median suture; drupaceous fruits indehiscent, often with persistent, reflexed flower parts; seeds in capsular fruits attached by a basal wing, seeds in drupaceous fruits unwinged, embedded in mucilaginous pulp.

Distribution

Guianas: present New World: present tropics and subtropics of both hemispheres: present
Mainly in the tropics and subtropics of both hemispheres; 23 genera with ca. 300 species, 12 genera in the New World, 11 of which in the Guianas with 40 species.

Taxonomy

  • Hippocrateoideae, characterized by capsular fruits consisting of 3 mericarps; seeds attached by a basal wing; wood without bands or islands of included phloem, but sometimes with a thick indented bark and on cross section often showing large rays that appear like spokes of a wheel (lens needed). In the Guianas: Anthodon, Cuervea, Elachyptera, Hippocratea, Hylenaea, Prionostemma and Pristimera.
  • Salacioideae, characterized by drupaceous, indehiscent fruits; unwinged seeds; wood often with wide, concentric rings of included phloem or with small phloem islands, and with narrow, inconspicuous rays. In the Guianas: Cheiloclinium, Peritassa, Salacia and Tontelea.

Wood

The two subfamilies, Hippocrateoideae and Salacioideae, distingui- shed by respectively capsular and drupaceous fruits, are also charac- terized by two types of wood structure. The main differences occur in the structure of the rays and in the absence or presence of an anomalous structure. In Hippocrateoideae rays are scarce, partly multi-seriate, at least 10 or more cells wide, whereas in Salacioideae rays are usually uniseriate, occasionally 2-3 cells wide and very numerous. Included phloem never occurs in Hippocrateoideae; in Salacioideae included phloem is often present as isolated "islands" or arranged in concentric rings, the rings sometimes inter-connected by extensions of the con- junctive parenchyma (visible with the naked eye on cross section).
Growth rings usually present, but vague and inconspicuous.
Vessels generally solitary, occasionally in radial multiples of 2-3, diffuse. Perforations simple. Intervascular pits alternate, oval to rounded, small, the slits often confluent, vessel-ray pitting identical.
Rays uni- or bi-seriate and 20-30-seriate (in Hippocrateoideae), hete- rogeneous, usually an irregular mixture of procumbent, square and upright cells; often very high; rhombic crystals usually present. Rows of unlignified cells occur in the growth ring margin in most of the genera of the Hippocrateoideae.
Parenchyma scarce, scanty vasicentric, and diffuse.
Ground tissue of non-septate fibre-tracheids and septate fibres, the two types either mixed or the septate fibres arranged in a parenchyma-like way as narrow, interrupted concentric bands and/or vasicentric, aliform-confluent.
Included phloem absent (in Hippocrateoideae) or present (in Salacioideae); if present it occurs either as isolated strands in diffuse or concentric arrangement or (more often) in conspicuous, concentric bands with or without radial or oblique interconnections of conjunctive tissue.

Notes

A short historical survey of the different opinions on the taxo- nomic position of the family seems desirable. The family Hippocrateaceae was established by A.L. de Jussieu in 1811. Subsequently most taxonomists accepted de Jussieu's concept. J.D. Hooker in Bentham & Hooker (1862), however, included the taxon as a tribe in Celastraceae. The latter had been created in 1814 by Robert Brown. Later monographers of New World Hippocrateaceae, like Miers (1872), Smith (1940) and Loesener (1942) followed de Jussieu. Loesener, however, attributed Cheiloclinium to Celastraceae, while Miers (1872) and Smith (1940) included the genus in Hippocrateaceae. Apart from Cheiloclinium, it is not difficult to separate the families Hippocrateaceae and Celastraceae as far as the New World species are con- cerned. Difficulties arise with regard to Asiatic and African taxa. Genera like Campylostemon and Kokoona seem to occupy a transi- tional position between the two families. Afterwards some more genera with transitional character states were described, viz. Brassiantha from New Guinea (Smith and Bailey, (1941) and Sarawakodendron from Malaysia (Ding Hou, 1967). Ding Hou in his treatment of Celastraceae in Flora Malesiana (1964) considered Hippocrateaceae as a subfamily. Cronquist (1981) is one of the taxonomists who does not accept the incorporation of Hippocrateaceae in Celastraceae. In the Flora of the Guianas the system of Cronquist is adopted. Consequently, the authors treat Hippocrateaceae as a separate family.
Celastraceae remain open for study by other enthusiastic botanists. Circumscription of genera within Hippocrateaceae also has aroused much discussion in the past. In the present treatment we follow Smith's (1940) revision in which 12 genera are recognized. Other authors accept only Hippocratea and Salacia (Robson, 1966), or several genera in the Hippoctateoideae and a more restricted number in Salacioideae (Macbride, 1951; Halle, 1962, 1978, 1981, 1983, 1986, 1990).
For more detailed information see Smith (1940), Ding Hou (1964) and Halle (several papers).