Abstract
Summary. Euphorbia cryptocaulis M. Gilbert and E. monadenioides M. Gilbert from Ethiopia are described as new. Both are geophytic and the status of subgenus Rhizanthium to which they would currently be considered to belong is discussed. It is suggested that the African species of Euphorbia fall into four major groups most practicably treated as subgenera at least for the present. Rhizanthium is an artificial group with members divided among three of the four subgenera recognised. One of these, subgenus Lacanthis (Rafin.) M. Gilbert, made up mainly of the Madagascan species formerly placed in 'sect. Diacanthium', is formally recognised for the first time. Euphorbia cryptocaulis M. Gilbert sp. nov. ab Euphorbia rubella Pax et E. brunellia Chiov., radice non tuberascenti, caulis tuberculis tenuibus, stipulis filiformibus, cymis laxioribus, pedunculis gracilioribus differt. Typus: Ethiopia, Corradi s.n. (holotypus FT). Glabrous hysteranthous geophyte: roots fibrous, not or only slightly thickened; stem vertical, completely below ground, cylindrical-ovoid, probably branching only after injury to apex, to 4 cm high, 2 cm diam., with c. 14 longitudinal rows of slender, recurved, soft, conical tubercles up to 5 mm long, extended into fine points, these set into tight rather irregular spirals towards the stem apex. Leaves inserted just above base of tubercles, closely resembling those of E. brunellii, forming a rosette flat on the ground; petiole up to 3 cm long depending on the depth of burial of the stem; lamina oblong-obovoid, up to 3-6 x 2-2 cm, base cuneate to rounded or subcordate, apex obtuse to shallowly emarginate, mucronulate, upper surface uniformly deep, slightly bluish-green, underside deep carmine red; stipules present, thread-like, up to c. 2 mm long, rapidly caducous. Cymes produced before leaves, very lax, to 12 cm long overall, branching at first dichasial but sometimes subsequently monochasial; peduncle filiform, c. 0-6 mm thick, up to 3-5-6 cm long, branches shorter; bracts forming asymmetric pairs immediately below sessile involucres, joined on upper side, free below, obovate, 2-4 x 2-1 mm, margin minutely toothed, pale pink. Involucres all bisexual, subcylindrical-obconical, 1-3 mm long, 2-1 mm diam. including glands; cyathial glands 6, separate, 4 larger oblong and 2 smaller square, pale pinkish green; scales between glands spathulate with fimbriate margin, that between the smaller glands rudimentary; bracteoles few in number, deeply divided into linear lobes. Male flowers in 5 groups of 3 per involucre, articulation exserted by 1 mm at anthesis; anther loculi subglobose, yellow. Female flower just exserted at anthesis, later recurved-pendulous; ovary deeply lobed with conspicuous grooves between loculi; styles bifid for half the-_ length then divided again just below apex, ultimate segments circinate. Fruit not seen. (Fig. 1 G-L).
Published Version
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