Acanthosicyos Welw. ex Benth. & Hook.f.
Acanthosicyos Welw. ex Hook.f., Gen. Pl. 1: 824. 1867.
Type: Acanthosicyos horridus F. Welwitsch 806 (LISU), Angola, Mossâmedes.
Up to 1 m high woody thorn-shrub with robust, angled branches and dioecious sex system. The leaves are reduced to small scale-like ovate, c. 2 mm long, bracts and the tendrils transformed into c. 1 cm long, straight thorns. The flowers are solitary (rarely the male flowers in fascicles), medium-sized, tomentose and ± sessile. Their receptacle-tube is turbinate with 5 short, inequal sepals (2 suborbicular to obcordate, 3 ovate). The 5 yellow petals are fused at the base, broadly-ovate, entire. The 3 stamens are inserted near the mouth of the tube with free, very short and fleshy filaments. Two anthers are bithecous, one monothecous with flexuous thecae. Their pollen is medium-sized (polar axis c. 68 µm, equatorial axis c. 70 µm), tricolporate and reticulate (Khunwasi 1998). The edible fruit is globose, verrucous, and indehiscent, ripening orange and contains many oblong, tumid seeds, 14-15 mm long and 9-11 mm broad with cream-coloured, crustaceous testa.
The single species of the genus is found in Angola, Namibia, Botswana, and the South African Republic, where it grows on dunes and riverbanks, sometimes forming stands of several meters in diameter.
Phylogenetically, the species is placed in tribe Benincaseae close to Raphidiocystis and Cephalopentandra (Schaefer & Renner 2011).
Acanthosicyos horridus Welw. ex Benth. & Hook.f., Gen. Pl. 1(3): 824. 1867 [as ‚horrida‘].
Khunwasi, C. 1998. Palynology of the Cucurbitaceae. Doctoral Dissertation Naturwiss. Fak., University of Innsbruck.
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.