Cereus columna-trajani Karwinsky in Pfeiffer, Enum. Cact. 76. 1837.
Cephalophorus columna-trajani Lemaire, Cact. Aliq. Nov. xii. 1838.
Pilocereus columna Lemaire, Cact. Gen. Nov. Sp. 9. 1839.
Pilocereus lateribarbatus Pfeiffer in Förster, Handb. Cact. ed. 2. 672. 1885.
Cephalocereus columna Schumann in Engler and Prantl, Pflanzenfam. 36: 182. 1894.
Pilocereus columna-trajani Schumann, Gesamtb. Kakteen 198. 1897, as synonym.
Plants erect, stout, up to 15 meters high, 4.5 to 5 dm. in diameter, often simple; ribs many, green; areoles oblong, bearing brown felt; radial spines 8 to 10, 12 to 25 mm. long; central spines more elongated, sometimes 16 cm. long, deflexed; spines all rigid, white or horn-colored except the brown bases and tips, sometimes said to he soft and erect; flowers described as purple.
Type locality: San Sebastian, Puebla, Mexico.
Distribution: Puebla and Oaxaca, Mexico.
In 1906, Dr. Rose collected in the Tomellin Canyon in southern Mexico, not far from the type locality of this species, what appeared to him to be this species. It forms forests which cover the surrounding hills, but, unfortunately, no flowers or fruit could be procured.
Melocactus columna-trajani (Pfeiffer, Enum. Cact. 46. 1837) is usually referred to this species, but is not formally published at the place here cited.
Cereus lateribarbatus (Rev. Hort. 1862: 427. 1862) belongs here, according to Lemaire.
Illustrations: Blanc, Cacti 77, f. 1715; Rev. Hort. 62: 129. f. 40, as Pilocereus co-lumna-trajani; Möllers Deutsche Gärt. Zeit. 29: 354. f. 9; MacDougal, Bot. N. Amer. Des. pl. 22, as Pilocereus tetetzo; Schelle, Handb. Kakteenk. f. 43, as Cephalocereus columna-trajani.
Plate xii is from a photograph taken by Dr. MacDougal at Tomellin Canyon, Mexico.
Cereus tetazo Coulter (Contr. U. S. Nat. Herb. 3: 409. 1896; Pilocereus tetetzo Weber in Schumann, Gesamtb. Kakteen 175. 1897), which we first confused with Pachycereus columna-trajani, is not of this genus, for its ovary is glabrous and the fruit more or less fleshy and edible. Coulter, however, does state that it is closely related, if not identical, with one of the species of this genus, that is, Pachycereus pecten-aboriginum. It should be compared with Cephalocereus macrocephalus.
10. LEPTOCEREUS (Berger) Britton and Rose, Contr. U. S. Nat. Herb. 12: 433. 1909.
Arborescent, bush-like, vine-like, or diffusely branching cacti; joints with 3 to 8 prominent, thin, high, crenate ribs, without aerial roots; spines slender, acicular; flowers diurnal, small; ovary spiny; flower-tube short, campanulate, spiny; stamens very numerous, borne at the base of the throat, scarcely exserted; stigma-lobes a little exceeding the stamens; fruit globose to oblong, more or less spiny, fleshy; seeds numerous, black.
Type species: Cereus assurgens Grisebach.
This genus is composed of eight species, six of them Cuban, one Santo Domingan, and one Porto Rican. Some are weak and clambering; others develop woody trunks. The branches are strongly ribbed and armed with clusters of long acicular spines. The earliest species were referred to Cereus. Leptocereus assurgens and L. quadricostatus, the only species known to Schumann, were placed by him in different sections of the genus Cereus, the former in his series Tortuosi and the latter in his series Oligogoni. A. Berger in his treatment of Cereus proposed the subgenus Leptocereus, which we afterward raised to generic rank. Cereus gonzalezi and C. tonduzii, also referred here by Berger, we have referred to other genera.
The generic name is from the Greek, signifying thin-cereus, referring to the thin ribs.
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