Euphorbia Cooperi, N.E. Br. ex Berger, Sukk. Euphorb. 83 and 84, Fig. 21;
Fl. Cap. vol. v. sect. 2, p. 368.
The genus Euphorbia is represented in South Africa by one hundred and eighty-three species, and we figure a representative of this genus for the first time. The genus contains many species which are of economic value as stock-food plants in the drier parts of the country, and among these may be mentioned E. esculenta, Marl. (Vingerpol), E. brachiata, E. Mey. (Soet or Blou Melkbos), E. coerulescens, Haw. (Soet Noorsdoring), and several other species which are commonly known as “Noorsdoring.�
The species figured here is one of the arborescent members of the family, and is found in Natal and in the Rustenburg and Piet Potgieter’s Rust Districts of the Transvaal. It is easily recognised by the continuous horny margins on the stems.
The plant when cut exudes a copious milky juice, which is a skin irritant, and which also causes a burning sensation in the throat if the air is inhaled when standing in close proximity to a bleeding plant.
Our plate was prepared from a plant growing at the Division of Botany, Pretoria.
Description:—A succulent leafless spiny tree, 10 to 15 ft. high; trunk becoming naked and cylindric below, 15 to 20 cm. thick; branches ascending, curved at their basal part, 5-to 6-angled, deeply constricted into conic-ovate or somewhat heart-shaped segments 5 to 15 cm. long, and 4 to 7·5 cm. in diameter, with the small central solid part not more than 2 to 2·5 cm. thick in the younger branches, glabrous;[{152}] angles wing-like, with triangular channels 2 to 4 cm. deep between them, their margins with a continuous horny nearly even grey border. Leaves rudimentary, scale-like, about 1 mm. long and 2 mm. broad, transverse, apiculate; spines 3 to 8 mm. long, in pairs 6 to 18 mm. apart, widely diverging, grey, with blackish tips; flowering-eyes 3 to 8 mm. above the spine-pairs; cymes 1 to 3 from the same eye, sessile, each with 3 involucres, glabrous. Bracts about 3 mm. long and 4 mm. broad, rounded, concave, usually minutely denticulate; involucres all sessile and the middle one male, lateral fertile, 5 to 6 mm. in diameter, cup-shaped, glabrous, with 5 glands and 5 erect short transversely rectangular fringed lobes; glands contiguous, 3 mm. in their greater diameter, narrowly transverse oblong, very minutely rugulose on the upper surface; capsule about 6 mm. long and 9 to 12 mm. in diameter, exserted on a stout pedicel, curved to one side, deeply 3-lobed seen from above, with laterally compressed lobes, glabrous, dark purple on the apex and along the angles, having a somewhat fleshy calyx at its base, with 3 deltoid-ovate acute lobes about 2 mm. long; cell-walls about 0·5 mm. thick, woody. Styles 2 mm. long, united for two-thirds of their length, with spreading arms, bifid at the apex; seeds 3 mm. in diameter, globose, with a raised line in a very slight furrow on one side, and a small pit at one end, light grey.
Plate 157.—Fig. 1, cross section of stem; Fig. 2, inflorescence; Fig. 3, male flowers; Fig. 4, male flower with fringed lobe; Fig. 5, gynaecium of female flower.
F.P.S.A., 1924.