PACHYCEREUS, 



69 



referred by us to Lemaireocereus, and by including ( 'ereus marginatus I h- 

 by him in liis subgenus Stenocereus. 



The name Pachycereus is from the Greek and means thick-cereus, 

 stout stems and branches. 



Key to Specifs. 



A. Scales of ovary and perianth-tube fleshy or herbaceous. 



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

 Perianth-tube broad; branches many-ribbed. 



Areoles of ovary and perianth-tube densely felted, but without long wool. 

 Joints green or but slightly glaucous. 



All areoles of the perianth-tube densely felted, the scales short. 



Spines brown to gray or sometimes black 1 . 



Spines of young growth yellowish brown 2. 



Upper areoles of perianth-tube little or scarcely felted, scales long. 



Flowering areoles bearing many short, weak spines 3. 



Flowering areoles bearing several acicular stiff spines 4. 



Young growth glaucous, the bloom persistent as whitish streaks 5. 



Areoles of ovary and perianth-tube bearing copious yellow-brown wool 1.5 



to 2.5 cm. long 6. 



Perianth-tube narrow; branches 5 to 7-angkd 7. 



Wool of ovary-areoles sparse, shorter than the coriaceous scales 8. 



AA. Scales of ovary and perianth-tube dry 9. 



AAA. Species not grouped; 10. 



1. Pachycereus pringlei( S.Watson) Brittonand 

 Rose, Contr. U. S. Nat. Herb. 12 : 422. 1909. 



Cereus pringlei S. Watson, Proc. Amer. 



Acad. 20:368. 1885. 

 Cereus calvus Engelmann in Coulter, Contr. 



U. S. Nat. Herb. 3: 409. 1896. 

 Cereus titan Engelmann in Coulter, Contr. 



U. S. Nat. Herb. 3: 409. 1896. 

 Pilocereus pringlei Weber, Diet. Hort. Bois 



966. 1 898, name only. 

 Pachycereus calvus Britton and Rose, Contr. 



U. S. Nat. Herb. 12: 420. 1909. 

 Pachycereus titan Britton and Rose, Contr. 



U. S. Nat. Herb. 12: 422. 1909. 



Tree-like, up to 11 meters high, usually 

 with a very short, thick trunk, sometimes 1 or 

 even 2 meters long or more, often 6 dm. but 

 sometimes 2 meters in diameter or more, very 

 woody and in age naked ; 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 1 1 to 

 15 but sometimes 17, obtuse; areoles, especially 

 the flowering ones, very large, brown-felted, 

 usually confluent or connected by a groove; 

 spines variable as to length, abundance, and 

 structure, usually more formidable in young 

 plants than in old plants, often wanting in very 

 old plants ; 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 sometimes for 2 meters, the areoles 

 becoming broad and uniting, often spineless; 

 flower-buds greenish; 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; seeds large, 

 edible. 



Candolle, placed 

 referring to the 



P. pringlei 

 I', orcuttii 



P. pecten-alioriginum 

 P. gaumeri 

 P. grandis 



P. chrysomallns 

 P. marginatus 

 P. ruficeps 

 P. lepidanlhus 

 P. columna-trajani 



