894 CONTRIBUTIONS FEOM THE NATIONAL HERBARIUM. 



8. PACHYCEREUS Britt. & Rose, Contr. U. S. Nat. Herb. 12: 420. 1909. 



Usually very large plants, more or less branched, with definite trunks, the 

 stems and branches stout, columnar, ribbed ; flowers diurnal, with rather short 

 tube ; outer perianth segments short, spatulate ; stamens included, numerous, in- 

 serted along the throat; style included; ovary and flower tube covered with 

 small scales bearing felt and bristles in their axils; fruit large, burlike, dry, 

 u&ually densely covered with clusters of deciduous spines and bristles; seeds 

 large and black. 



One other species is known, a native of Guatemala. 



Wool of ovary areoles sparse, shorter than the coriaceous scales — 8. P. ruficeps. 

 Wool of ovary areoles copious, mostly longer than the scales. 



Perianth tube narrow ; branches 5 to 7-angled 7. P. marginatus. 



Perianth tube broad; branches many-ribbed. 

 Areoles of ovary and perianth tube bearing copious yellow-brown wool 



1.5 to 2.5 cm. long 6. P. chrysomallus. 



Areoles of ovary and perianth tube densely felted but without long wooL 

 Joints, at least the young ones, glaucous, the bloom persistent as whitish 



streaks 5. P. grandis. 



Joints green or but slightly glaucous. 



Upper areoles of the perianth tube, like the others, densely felted, the 

 scales short. 



Spines brown to gray or sometimes black 1. P. pringlei. 



Spines of young growth yellow-brown 2. P. orcuttii. 



Upper areoles of the perianth tube little or scarcely felted, the scales 

 long. 

 Flowering areoles bearing many short weak spines. 



3. P. pecten-aboriginum.. 

 Flowering areoles bearing several stiff acicular spines_4. P. gaumeri. 

 1. Pachycereus pringlei (S. Wats.) Britt. & Rose, Contr. U. S. Nat. Herb. 

 12: 422. 1909. 

 Cereus pringlei S. Wats. Proc. Amer. Acad. 20: 368. 1885. 

 Cereus calvus Engelm. ; Coulter, Contr. U. S. Herb. 3: 409. 1896. 

 Cereus titan Engelm.; Coulter, Contr. U. S. Nat. Herb. 3: 409. 1896. 

 Sonora and Baja California ; type from the Altar River, Sonora. 

 Treelike, up to 11 meters high, usually with a very short thick trunk, some- 

 times 1 or even 2 meters long or more, often 60 cm. in diameter or more; 

 stem sometimes nearly simple but often with numerous thick upright branches, 

 more or less glaucous, very spiny or in some forms nearly naked ; ribs usually 

 11 to 15 but sometimes 17, obtuse; areoles, especially the flowering ones, very 

 large, brown-felted, usually confluent or connected by a groove; spines on 

 young growth 20 or more at an areole, 1 to 2 cm. long, white but with black 

 tips, or on young plants sometimes 12 cm. long and black throughout ; flower- 

 bearing region of the branches extending from near the top downward some- 

 times for 2 meters, the areoles becoming broad and uniting, often spineless; 

 flowers 6 to 8 cm. long, the tube and ovary bearing small acute scales, these 

 nearly hidden by the mass of brown hairs produced in their axils ; inner 

 perianth segments white, broad, spreading ; fruit globular, covered with brown 

 felt and bristles, dry. "Card6n", "card6n pelon" ; "saguesa" (Sonora). 



This is an abundant and conspicuous plant in many parts of Sonora and 

 Baja California, often forming extensive forests. The dried wood is employed 

 for fuel, and the stems for building huts. The Indians grind the pulp and 



