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Gerrardanthus | Cucurbitaceae

Gerrardanthus.

Gerrardanthus Harv. ex Hook. f.
Gerrardanthus Harv. ex Hook. f. in Benth. & Hook., Gen. Pl. 1: 820, 840. 1867.
Type: Gerrardanthus macrorhizus Harv. ex Benth. & Hook.f., W.T. Gerrard 342 (K, P), Zululand, South Africa.
Atheranthera Masters in D. Oliver, Fl. Trop. Afr. 2: 519. 1

Climbers with herbaceous or softly woody, up to 15 m long shoots and perennial tuberous rootstocks, often as partly exposed pachypodia (up to 1.8 m across). The sex system is dioecious. The leaves are petiolate, ovate-cordate, unlobed or palmately 3-5-lobed, the tendrils are apically bifid. The flowers are small. Male flowers are produced in axillary panicles, female flowers solitary or in small groups. The receptacle-tube is broad, saucer-shaped with five small, ovate or triangular sepals. The corolla is regular to strongly zygomorphic with five free, unequal, yellowish to orange-brown petals. The 4-5 stamens are inserted near the center of the tube on free filaments. The anthers are all monothecous, two pairs or two pairs and one single. The thecae are straight, horizontal with tricolporate, striate or reticulate, small to medium-sized pollen (polar axis 34-50 µm, equatorial axis 26-52 µm (Khunwasi 1998)). The ovary is 3-sided, 3-locular at the apex and 1-locular at the base with three placentae and several, pendent ovules. The three divergent styles carry reniform, bilobed stigmata. The fruit is a pale yellow, dry, obconic-cylindric, 3-sided capsule, dehiscing by an apical triradiate slit. The seeds are fusiform with (pale) brown testa. The body is up to 2 cm long, the distal, membranous wing also up to 2 cm. Germination is epigeous (Zimmermann 1922).

Five species in lowland rainforest, deciduous bushland and wooded grassland of tropical Africa and South Africa. Named after the British plant hunter William Tyrer Gerrard (ca. 1831-1866).

Phylogenetically, Gerrardanthus is placed in tribe Zanonieae, where it groups as sister to a clade consisting of Zanonia, Siolmatra and Xerosicyos (Schaefer & Renner 2011).

Accepted species

Gerrardanthus grandiflorus Gilg ex Cogn., Pflanzenr. IV, 275 I: 22. 1916.
Gerrardanthus lobatus (Cogn.) C. Jeffrey, Kew Bull. 15: 353. 1962.
Gerrardanthus macrorhizus Harv. ex Benth. & Hook.f., Gen. Pl. 1: 840. 1867.
Gerrardanthus paniculatus (Mast.) Cogn., Pflanzenr. IV, 275 I: 20. 1916.
Gerrardanthus tomentosus Hook.f., Bot. Mag. 109: t. 6694. 1883.

Literature

Crouch, N., Prentice, C., Smith, G. F., and R. Symmonds. 1999. South Africa’s rarest caudiciform cucurbit, Gerrardanthus tomentosus. Bradleya 17: 95-100.

Jeffrey, C. 1967. Cucurbitaceae, in E. Milne-Redhead and R. M. Polhill, Flora of Tropical East Africa.

Khunwasi, C. 1998. Palynology of the Cucurbitaceae. Doctoral Dissertation Naturwiss. Fak., University of Innsbruck.

Powell, D. R. 1976. Some unusual succulents. Bull. Afr. Succ. Pl. Soc. 10: 139-141.

Schaefer, H. and S.S. Renner. 2011. Phylogenetic relationships in the order Cucurbitales and a new classification of the gourd family (Cucurbitaceae). Taxon 60: 122-138.

Zimmermann, A. 1922. Die Cucurbitaceen. Beiträge zur Anatomie, Physiologie, Morphologie, Biologie, Pathologie und Systematik. Vols. 1 and 2. Jena: Fischer.