896 CONTRIBUTIONS FEOM THE NATIONAL HEEBAEIUM. 



simple, becoming erect almost from the first, with numerous constrictions, 

 pale green or when young glaucous, with some bloom persisting in streaks ; 

 ribs 9 to 11, acutish, high; sterile areoles circular, large, bearing white felt 

 and subulate spines, 2 to 3 cm. apart, not running together; old spines grayish 

 to white with black tips; radial spines 9 or 10; central spines 3, the lower 

 one longer, sometimes 6 cm. long, somewhat flattened ; flowering areoles large, 

 elliptic, bearing acicular or bristle-lilie spines ; flowers about 4 cm. long ; ovary 

 and flower tube bearing small, acuminate scales, their axils filled with downy 

 hairs; fruit large, globular, dry, covered with long yellow bristles and 

 yellow felt. 



6. Pachycereus chrysomallus (Lem.) Britt. & Rose, Contr. U. S. Nat. Herb. 



12: 421. 1909. 



Pilocereus chrysomallus Lem. Fl. Serr. Jard. 3: under pi. 2-'f2. 1847. 



Cereus chrysomallus Hemsl. Biol. Centr. Amer. Bot. 1: 541. 1880. 



Pilocereus fulviceps Weber; Schum. Gesamtb. Kakt. 176. 1897. 



Puebla and Oaxaca. 



Stem columnar, massive, at first simple, but in very old plants much 

 branched, giving off hundreds of erect branches which form an almost com- 

 pact cylinder up to 5 meters in diameter, becoming 12 to 18 meters high ; 

 branches glaucous green, 11 to 14-ribbed ; flowering branches capped by dense 

 masses of brownish wool ; areoles approximate or even confluent ; radial 

 spines about 12, slender; centx'als 3, 1 very long, sometimes 12 to 13 cm. long; 

 flowers borne near the tops of the stems or branches, 6 to 7 cm. long, the 

 bud, afterward the flower, and finally the fruit, completely concealed in the 

 long wool ; ovary covered with small pale, imbricate scales ; flower tube also 

 covered with imbricate scales, but these larger and pinkish, pointed ; flower 

 tube proper 10 mm. long or less ; throat funnelform, 3 cm. long ; inner perianth 

 segments numerous, 1.5 to 3 cm. long, cream-colored. 



7. Pachycereus marginatus (DC.) Britt. & Rose, Contr. U. S. Nat. Herb. 



12: 421. 1909. 



Cereus marginatus DC. Mem. Mus. Hist. Nat, 17: 116. 1828. 



Cereus gemmatus Zucc. ; Pfeiff. Enum. Cact. 96. 1837. 



Hidalgo, Quergtaro, and Guanajuato; also planted and naturalized in other 

 parts of Mexico. 



Stems 3 to 7 meters high, erect, usually simple; ribs 5 or 6 (7 in the original 

 specimen), somewhat acute when young, obtuse in age; areoles close together, 

 usually confluent, their wool forming a dense white cushion along the ridge of 

 each rib; spines at first 5 to 8 (1 central), in old areoles more numerous, 1 cm. 

 long or less, but in flowering areoles often numerous, bristly and 2 cm. long; 

 flowers and fruit usually closely set, one above the other, apparently only one 

 at an areole, but recorded as often geminate, and appearing anywhere along the 

 ribs from the top downward ; flower funnelform, 3 to 4 cm. long ; tube and 

 ovary more or less scurfy and with ovate scales subtending bunches of wool 

 and small spines; fruit globular, about 4 cm. in diameter, not very fleshy, yel- 

 lowish red within, covered with spines and wool which finally drop off; seeds 

 numerous, black, somewhat shining, 4 mm. long. " Organo " (Durango, Oaxaca, 

 San Luis Potosl) ; " jarritos" (flowers; San Luis PotosI). 



Palmer reports that the flowers are sold in the markets of San Luis Potosl for 

 the honey which they contain. This species, like many other cacti of similar 

 habit, is much planted to form living fences. The straight trunks are placed 

 closely side by side and form impenetrable barriers, which are characteristic 

 features of Mexican towns. 



