The true plant is figured and described by Jackson as an erect tree, with a stout short woody trunk, and very numerous upcurved long sparingly divided branches, the whole resembling a candelabrum. The angles of the branches are armed with short spines, and the flowers are produced from the tips of the young shoots. The thorns adhere to everything that touches them, and he supposes them to have been intended by nature ‘to prevent cattle from eating this caustic plant, which they always avoid on account of its prickles.’ The juice flows from incisions made with a knife, and hardens and drops off in September. The plants, he says, produce abundantly once only in four years, and the fourth year’s produce is more than all Europe can consume. The people who collect the gum are obliged to tie a cloth over their mouths and nostrils, to prevent the small dusty particles from annoying them, as they produce incessant sneezing.
The history of the Euphorbium as given in the ‘Pharmacographia’ is, that it was known to both Dioscorides and Pliny as a native of the Atlas, and was named in honour of Euphorbus, physician to the learned King Juba II. of Mauritania, himself the author of treatises on Opium and Euphorbium.
The prevalence of cactoid Euphorbiæ in Marocco, of which there are three species in the southern districts, is a similar instance to that of the Argan, of tropical forms advancing far north in the extreme west of the old world; and as the Argan has its nearest ally in Madeira, so have the Maroccan Euphorbiums close congeners in the Canary Islands. All these belong to the section Diacanthium of Boissier, of which the other species are Abyssinian, Arabian, Indian, and South African.
Gum Euphorbium was extensively used by early practitioners as an emetic and purgative, and was exported in large quantities; now, however, the trade in it is rapidly declining, and we were informed that it is chiefly used in veterinary practice, and as an ingredient in a paint for the preservation of ships’ bottoms.
Euphorbia resinifera is in cultivation at Kew, where specimens may be seen both in the Succulent-plant House and Economic-plant House.
The Arar, Thuja or Gum Sandrac Tree.
Callitris quadrivalvis.—Ventenat, Nov. Gen. Decad. 10; Richard, Conif. 46, t. 8, f. 1; Endlich, Synops. Conif. 41; Parlatore, in DC. Prod. xvi. pars 2, 452; Ball, in Journ. Linn. Soc. Bot. xvi., 670.
Thuja articulata.—Shaw’s ‘Travels in Barbary,’ 462, with a plate; Vahl, Symb. ii. 96, t. 48; Desf. Flor. Atlant. ii. 353, t. 252.
Frenela Fontanesii.—Mirbel, in Mem. Mus. xiii. 74.
This tree is a native of the mountains of North Africa, from the Atlantic to Eastern Algeria; but we are not aware whether its eastern limit has ever been accurately determined. It has no congener, its nearest ally being a South African genus of Cypresses (Widdringtonia), of which several species are recorded from the Cape Colony, Natal, and Madagascar, and which differ in having alternate leaves and many ovules to each scale.