JStenadenlnm,] cxxii. euphorbiacej2 (brown). 449 



base, and cut into a fringe of filiform segments at the top, with an 

 erect oblong entire lobe outside and behind, glandular at its apex and 

 overtopping the fringe. Stamens (really male flowers, as in Enphorbiay 

 without a perianth) numerous, in 5 groups, contained in 5 pocket-like 

 cavities at the base of each lobe of the involucre, not mingled with 

 bracteoles, but the membranous partitions separating the groups Hnd 

 surrounding the pedicel of the female flower are produced into a few 

 filiform pubescent segments ; anthers small, rather broader than lon<r. 

 Ovary (really a female flower, as in Euphorbia) without a perianth 

 at its base, pedicellate, surrounded by the stamens, exserted from 

 the opening in front of the involucre and recurved, 8-celled, with 

 one ovule pendulous from the apex of the inner angle of each 

 cell ; styles o, united below, free above. Capsule :^-angled. Seeds 

 oblong, truncate at each end, 4-angled, carunculate. — A succulent 

 shrub with spiny branches, apparently leafless at the time of flowering. 

 Leaves alternate, not seen. Flowers in dense many-flowered cymes 

 on stout peduncles. Bracts in pairs, connate at the base into 

 an oblique cup-like 2-lobed body (bract-cup) enclosing the involucres 

 or nearly free and embracing the branches at the forkings of the 

 cyme, keeled on the back. 



iSpecies 1, endemic. 



The structure of the involucre of this remarkable plant clearly demonstrates the 

 fact that the involucre of Euphorbia and allied genera is formed by the fusion of 

 two series of bracts. In Siena denium the outer series is reduced to ore bract which 

 is free nearly to the base, the greater part of the involucre being formed by the inner 

 series alone. 



1. S. spinescens, Pax in Engl. JaJirh. xxx. o4;>. A succulent 

 shrub 6-1) ft. high, spiny, leafless at the time of flowering. Branches 

 ^-J in. thick, glabrous, armed under each leaf-scar with :> spreading 

 light brown spines, middle one J- J in. long, very stout, usually slightly 

 recurved, lateral pair smaller, sometimes obsolete, usually 1-3J lin. 

 long. Leaves not seen. Peduncles 2-3 at the apex of the branches, 

 erect, 3-4J in. long, flattened, acutely 2-edged, 2i-4j lin. broad, with 

 a pair of widely spreading spines at the apex, glabrous, terminating 

 in 1 or '1 repeatedly forked dense cymes 1J-2J in. in diam., with 

 puberulous branches J in. thick. Bracts about \ in. long, 2-oJ lin. 

 broad, broadly ovate, obtuse, apiculate, keeled down the back, 

 puberulous oji both sides, apparently whitish, those enclosing the 

 involucres connate for about half their length behind, the others more 

 or less free and the pair at the base of the cyme adnate to a short stout 

 spine immediately beneath. Involucre o-dh lin. long, white-pubescent, 

 with the segments of the marginal fringe li— 2 lin. long, and the 

 entire dorsal lobe or gland 2-2J lin. long and 1^ lin. broad, oblong, 

 broadly rounded or subtruncate" at the apex, puberulous. Ovary and 

 capsule exserted and recurved, the former white-tomentose, the latter 

 3J lin. long, o lin. in diam., oblong, somewhat truncate at each end, 

 acutely :3-angled, puberulous; styles IJ lin. long, united at the base, 

 thickened and bifid at the apex, pubescent. 



