This section is from the book "The Standard Cyclopedia Of Horticulture Vol2", by L. H. Bailey. See also: Western Garden Book: More than 8,000 Plants - The Right Plants for Your Climate - Tips from Western Garden Experts.
Branching shrub, with 6-angled stem, branches ascending, about 2 in. thick, 5- or more-angled: spine pairs less than 1/2in. apart; spines 1/2in. long, red to gray. Morocco. G.Z. 1904:122.
hh. Sides of mature branches concave, angles more or less winged, branches often 3-4 in. thick.
Tree-like: stem at first 6-angled, later cylindrical: branches whorled, divergent, then ascending, 3-5-angled, 2-4 in. thick; joints 2-12 in. long; spine pairs 3-9 lines apart; spines less than 5 lines long; spine-shields united only on stronger shoots: leaves small, roundish. S. Africa(?).
Tree-like: whorled ascending branches, 3-5 in. thick, the joints broad at base and tapering upward, 6-angled, spines 5 lines long, black to gray. Natal. - A fine species.
GG. Spine-shields separate. See also No. 28.
h. Sides of mature branches plane or slightly convex, angles not winged, branches less than 2 in. thick.
(E. San Salvador, Hort.). A much-branched shrub: branches 4-angled, spine-shields triangular-rounded, small, 3-5 lines apart. S.W. Morocco. G.Z. 19:102. - This species yields the euphor-bium gum of the ancients.
Shrub or tree, 12-20 ft. high, with many 4-6-angled, suberect, not conspicuously jointed branches, as much as 3 in. thick; angles sub-entire; spines 2 lines long, black: leaves almost none. Canary Isls. Gn. 53, p. 46. - This is one of the most common succulent euphorbias. It is easy to grow and prop, readily from cuttings, as well as from seeds which are frequently produced in cultivation Several other species are in cult, under this name.
hh. Sides of branches concave to deeply grooved between the ribs, which are more or less winged; branches 2-6 in. thick. (The species of this group and several others, e. g. E. tenebrosa, N. E. Br., E. acrurensis, N. E. Br., E. grandis, Lem. (E. neutra, Berger), E. controversa, N. E. Br., E. Erythraea N. E. Br., are in cultivation, probably some in Amer., as E. abyssinica or some as E. candelabrum. The true E. abyssinica, Gmel., is not in cultivation)
(E. abyssinica, Berger, not Gmel.). Tree: branches 5-8-angled, joints 4-12 in. long,
4-5 in. thick, the conspicuous wings marked by swollen veins; spine pairs 1 in. apart, sunken; spines stout, brown, 1-2 lines long: leaves narrow, 1 in. or more long: flowering eye above the spine-shield. N.Africa G.C. III. 20:497. Gn. 52, p. 106.
Differs from E. neglecta in branches 5-angled: spine pairs on apex of a recurved tooth: leaves shorter; spines darker; veins in wings not prominent. Natal (?).
(E. candelabrum, Berger, not Trem., see No. 24). Tree, with 4-5-angled stem and branches, slightly jointed: spine pairs 8-10 lines apart; spines 3-5 lines long, stout, dark brown to gray: flowering eye included in the spine-shield. Abyssinia.
ffff. Angles of branches 9-13.
G. Spine-shields almost always united into a horny margin; grooves between ribs rather shallow: branches about 2 in. thick.
A shrub to 9 ft. high: branches erect, 9-10-angled; spines short, spreading, red when young. Morocco. J.H. III. 59:627.
Shrub: branches 9-13-angled; spines but little spreading, yellowish to gray, 3-6 lines long: leaves minute. N. Africa R.H. 1875, pp. 336-7.
gg. Spine-shields often isolated; grooves between ribs very deep.
Low shrub: branches erect, scarcely jointed, 6-9 lines thick, 10-13-ribbed; spines 6-9 lines long, spreading, brown when young. Arabia.
38. Pfersdorfii, Hort. Trunk round. 1 1/2-2 1/2 in. thick, 9-angled, much branched when old: spines large, 4-9 lines long. - A species not very well known.
dd. Spines, if any, not in stipular position. Subsection Treisia.
e. Podaria in longitudinal rows or ribs.
F. Body cylindrical: sterile infloresence transformed into thorns.
Class Anthacantha. g. Ribs without prominent cross furrows between podaria.
stem 3-4 ft. high, over 1 in. thick, candelabraform-branched, 5-8-ribbed: ribs broader than high; thorns not numerous, strong, yellow, 3/4in. long: leaves linear-lanceolate, acute. Cape of Good Hope. - According to N. E. Brown the plants of this section and their names are much confused in cult, and without careful study it would be difficult to say just what is being grown under the names of E. hep-tagona, E. mammillaris, E. enopla, etc.
(E. enneagona, Haw.). stem erect, 2-3 ft. high: branches with 9-13 straight ribs, the podaria forming declined teeth: leaves small, triangular;
thorns numerous, 4-7 lines long. Cape region. - Cuttings from the branches have a different form from seedlings.
stem up to 5 ft. high, 5 in. thick, 10-13-ribbed, the ribs high and narrow, often somewhat spiral: thorns 4-5 lines long; leaves minute. Cape region.
gg. Ribs with the podaria separated by cross furrows.
Low: branches 7-12-ribbed, about 1 in. thick; ribs flat; podaria not prominent; zones of spines up to 1 in. long, alternate with areas free from them. Cape region. variety spinosior, Berger, is more vigorous and spiny, with more prominent podaria.
stem irregularly branched, 1 in. thick: branches with about 5-8 straight ribs, 2 lines high; podaria forming pointed tubercles: leaves linear; thorns numerous on strong branches, few on others. Cape region(?). - Grown as E. mexicana, E. imbricata, and E. cereiformis.
ff. Body spherical, not thorny.