THE CACTACEAE. 



Curiously enough, the type species is one of the species of Linnaeus which Miller omits 

 in his Gardener's Dictionary (1768). 



Cereus pellucidus Pfeiffer (Enum. Cact. 108. 1837), which we formerly referred to this 

 genus (Contr. U. S. Nat. Herb. 12: 432), following previous authors, is to be looked for in 

 Leptocereus. Both Schumann and Berger regard this group as consisting of but a single 

 species, the former placing it with Cereus greggii in his series Acutangules, and the latter in a 

 subsection Acanthocereus; Pfeiffer, on the other hand, recognized several species as belonging 

 to this group ; we distinguish at least 7. The name is from the Greek, meaning thorn-cereus. 



Key to Species. 



Ribs usually 3, rarely 4, thick. 



Joints 8 to 10 cm. wide, dee'ply crenate; spines very stout, subulate. 



Spines 1 to 6; perianth-tube about 7 cm. long 1. A. horridus 



Spines about 10, the outer 5 to 8, very short; perianth-tube about 12 cm. long 2. A. colombiamis 



Joints 2 to 8 cm. wide, low-crenate; spines slender. 



Spines well developed, subulate 3. A. pentagomis 



Spines short or none, when present acicular 4. A. subinermis 



Ribs 4 to 7, mostly thin. 



Plants green. 



Spines up to 7 cm. long; ribs 3 to 5 5- A. occidentdhs 



Spines 3 cm. long or less ; ribs 5 to 7 6. A . brasiliensis 



Plants bluish white; joints 4-angled; spines 2 to 6, the longest 2 cm. long 7. A. albicaulis 



1. Acanthocereus horridus sp. nov. 



Plants stout, the joints strongly 3-angled or 3-winged, the young growth 5 or 6-angled; wings 

 with deep undulations; areoles large, 3 to 6 cm. apart; spines brown or blackish when young; radial 

 spines 1 to 6, very short, conic, less than 1 cm. long; central spine usually 1, sometimes 2, often very 

 stout and elongated, sometimes 8 cm. long; flower, including the ovary, 18 to 20 cm. long; tube 4 

 cm. long, including the funnelform throat 12 cm. long; throat 4 cm. broad at mouth; outer perianth- 

 segments linear, brown or greenish, 6 cm. long; inner perianth-segments 3 to 4 cm. long; stamens 

 white; style thick, cream-colored; fruit 3.5 cm. long, light red, glossy, covered with large areoles 

 bearing white felt; skin thick, finally splitting as the 

 fruit ripens; pulp red. 



Collected in Guatemala by F. Eichlam in 

 1909 (New York Botanical Garden No. 34788). 

 It has frequently flowered in cultivation, both 

 at Washington and at New York. 



Here we are disposed to refer E. W. Nelson's 

 plant from San Juan Guichicovi, Oaxaca, Mex- 

 ico, collected June 21 to 24, 1895 (No. 2729). 



Figure 181 shows a part of a joint of the 

 type specimen. 



2. Acanthocereus colombiamis sp. nov. 



Erect, branching dichotomously, 2 to 3 meters 

 high; joints about 9 cm. wide, strongly 3-winged; 

 areoles large, 5 cm. apart; radial spines 5 to 8, very 

 short, less than 5 mm. long; central spines 1 or 2, 

 very stout, 4 to 5.5 cm. long; flower 25 cm. long, 

 white, with a rather stout tube 12 cm. long, the 

 gradually expanded throat 5 to 6 cm. long. 



Collected by Francis W. Pennell and Henry 

 H. Rusby near Calamar, Colombia, July 10, 

 1917 (No. 23, type), and by Herbert H. Smith 

 near Bonda, Colombia, in 1 898-1 899 (No. 2423). 

 grows in dry forests and thickets at low altitudes; here it is known as pitahaya.* His 



*Pitahaya is a well-known name in tropical America for many species of cacti, especially of Cereus and its 

 relatives, of which there are various spellings, such as pitajaya, pitajuia, pitalla, pitaya, and pithaya. Several suf- 

 fixes are sometimes used with it, as pitahaya agre, pitahaya agria, pitahaya de San Juan, and pitahaya dulce, and 

 it has the diminutives pitayita and pttahayita. 



Fig. 181. — Part of joint of A. horridus. X0.4. 



According to Mr. Smith this species 



