68 



THE CACTACEAE. 



Type locality: Rocky sandy bottoms near Mollendo, southern Peru. 



Distribution: Foothills of southern Peru, altitude 600 meters. 



This plant is very abundant in the foothills of southern Peru. In many places it is 

 the only conspicuous plant in this arid region, which in the dry season is otherwise almost 

 devoid of plant life. In the shelter of these plants thousands of lizards live and, doubtless, 

 feed upon the flowers. Dr. Rose collected the species in 1914 (No. 18810) at Posco, Peru, 

 not far from the type locality. 



Fig. ioi. — Flower of C. brevistylus. X0.7. 



Fig. 102. — Flower of C. 

 brachypetalus. X0.7. 



Fig. 103. — Fruit of Corryocactus 

 brachypetalus. X0.7. 



Figure 102 represents a flower and figure 103 a fruit, collected by Dr. Rose at Posco, 

 Peru, in 1914; figure 100 is from a photograph taken near Posco, Peru, by T. A. Corry in 

 1918. 

 3. Corryocactus melanotrichus (Schumann). 



Cereus melanotrichus Schumann, Gesamtb. Kakteen 71. 1897.* 



Plant 1 to 2 meters high, forming small clumps with erect slender branches 3 to 4 cm. in diameter ; 

 ribs 7 or 8, much lower than in the other species; areoles 1 to 1.5 cm. apart, black or nearly so; spines 

 7 to 15, light yellow, subulate, somewhat unequal, the longest ones 5 to 7 cm. long; flowers broadly 

 funnelform, 6 to 8 cm. long, 5 to 7 cm. broad; perianth-segments yellow; filaments much longer 

 than in the other species; areoles of the flower with 1 to 5 long, black, bristle-like spines ; fruit globular, 

 5 to 6 cm. in diameter, very juicy, covered with clusters of small acicular spines. 



Type locality: Near La Paz, Bolivia. 



Distribution : Central Bolivia, altitude 3,300 meters. 



Plants of this species are much smaller than those of the other two and often form low 

 thickets, growing on the barren hills in and about Ea Paz. The species was re-collected 

 by Dr. Rose in 1914 (No. li 



9. PACHYCEREUS (Berger) Britton and 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 tubes; outer perianth-segments short, 

 spatulate; stamens included, numerous, inserted along the throat; style included; ovary and flower- 

 tube covered with small scales bearing felt and bristles in their axils; fruit large, bur-like, dry, usually 

 densely covered with clusters of deciduous spines and bristles; seeds large and black. 



Type species : Cereus pringlei S. Watson. 



We recognize 10 species, all natives of Mexico, from northern Sonora to Yucatan. The 

 name was first used by Berger as a subgenus of Cereus (Rep. Mo. Bot. Gard. 16: 63. 1905) ; 

 we agree with his limitation of the group, except by excluding Cereus thurberi Engelmann, 



*Thisname occurred in print two years earlier, but without description,' in the Memoirs Torrey Botanical Club 

 (4:207). 



