BRITTON AND ROSE—CEREUS AND ITS ALLIES. 421 
Pachycereus chrysomallus (Lem. ) Puate LX VI. 
Cephalocereus chrysomallus (Lem.) Schum. in Engl. & Prantl, Pflanzenfam. 3%: 
182. 1894. 
Pilocereus chrysomalius Lem. Fl. Serres 3: sub pl. 242. 1847. 
Cereus chrysomallus Hemsl. Biol. Centr. 1: 541, 1880. 
Pilocereus fulviceps Weber; Schum. Gesamtb. Kakteen 176. 1899. 
Cereus fulviceps Berger, Ann. Rep. Mo. Bot. Gard. 16: 64. 1905. 
Pilocereus rupiceps Weber; Gosselin, Bull. Mus. Paris 11: 506, 1905. 
TYPE LocaLity: In Mexico. 
Distrisution: Puebla and Oaxaca, Mexico. 
ILtLustRATIONs: Contr. Nat. Herb. 10: pl. 18; MacDougal, Bot. N. Am. Deserts 
pl. 16. 
EXPLANATION OF PLATE LX VI.—From a photograph taken by Dr. D. T. MacDougal. 
Pachycereus columna-trajani (Karw.). 
Cephalocereus columna-trajani (Karw.) Schum. in Engl. & Prantl, Pflanzenfam. 3%: 
182. 1894, 
Cereus columna-trajant Karw.; Pfeiff. Enum. Cact. 76. 1837. 
Pilocereus columna Lem. Cact. Gen. & Sp. 9. 1839. 
Pilocereus lateribarbatus Pfeiff.; Rumpl. Forst. Handb. Cact. ed. 2. 672. 1886. 
Cereus tetazo Coult. Contr. Nat. Herb. 3: 409. 1896. 
Pilocereus tetetzo Weber; Schum. Gesamtb. Kakteen 175. 1899. 
Type Locairy: San Sebastiin, Puebla, Mexico. 
Disrripution: Puebla and Oaxaca, Mexico. 
Ituustrations: Rev. Hortic. 1890: 129. f. 40; MacDougal, Bot. N. Am. Deserts 
pl. 22. 
Pachycereus grandis Rose, sp. nov. 
Large plants 6 to 10 meters high, often with a single erect trunk but generally, 
especially in old plants, much branched near the base, the trunk sometimes 1 meter 
in diameter; branches columnar and generally simple, becoming erect almost from 
the first, repeatedly constricted (this especially noticeable from a distance), pale 
green in color; ribs 9, 10, or 11, acute; areoles 2 to 3 cm. apart, not running together 
nor extending below the spines as in 2. pecten-aboriginum; old spines grayish or 
white with black tips; radial spines 9 or 10; centrals 3, the lower one longer (some- 
times 6 cm. long), somewhat flattened laterally, the two upper opposite, similar to 
the radial; flowering areoles very large, elliptical, 2 em. long, thickly set below with 
stout brown bristles, in the upper half with short yellow bristles; flowers rather 
small, about 4 cm. long; ovary and corolla tube covered with tawny wool; fruit 
large, globular, dry, covered with long yellow bristles and yellowish wool. 
Collected on the pedregal near Cuernavaca by J. N. Rose and J. 8. Rose, August 
14, 1906 (no. 11087). . 
Type U. 8. National Herbarium no. 453872. 
This giant cactus is common on the edge of the pedregal near Cuernavaca and 
extends for many miles down the valley southward. 
The species is near P. pecten-aboriginuim but is generally more branched and prob- 
ably larger. Technically, it has very different areoles and much longer spines. 
Pachycereus marginatus (DC.). 
Cereus marginatus DC. Mem. Mus. Paris 17: 116, 1828. 
Cereus gemmatus Zace.; Pfeiff. Enum. Cact. 96. 1857. 
Type LocaLity: Mexico. 
DisrrisutTion: Hidalgo, Querétaro, and Guanajuato, Mexico. 
ILLustRAtIoNs: Contr. Nat. Herb. 5: pl. 59, 60. 
