438 



CONTEIBUTIONS FROM THE NATIONAL HEKBAEIUM. 



Joints large, 10 cm. long or more, nearly cylindric, 

 3 to 4 cm. in diameter (strongly tuberculate); 

 epiaes 3 to 5 cm. long, yellowish brown (flat- 

 tened, stout) 4. 0. stanlyi. 



Joints smaller, rarely over 5 cm. long, clavate; 

 spines various but not yellowish. 

 Spines 3 to 5 cm. long, straight, slender, terete, 

 ashy gray; joints rather slender, about 15 



mm. in diameter 5. 0. grahami. 



Spines shorter, 2 cm. long or less, one stout and 



flattened, white, strongly recurved 6. 0. clavata. 



Joints cylindric, more or less strongly tuberculate; spines 



inclosed in a chartaceous sheath; plants mostly taller, 



60 cm. to 3 meters or more. 



Plants diffuse, about 60 cm. high, seldom more; stems 



10 to 15 mm. in diameter; flowers yellow. 



Sheaths pale yellowish to white; plant of western 



New Mexico and Arizona 7. 0. whippld. 



Sheaths yellowish brown; plant of eastern New 



Mexico and Texas 8. 0. davisii. 



Plants taller, branching from a simple or divided main 

 stem, 1 to 3 meters high or more; flowers mostly 

 purple, yellow in 0. leptocaulis. 

 Stems slender, 1 cm. in diameter or less; plants 

 about 1 meter high when full grown; spines 

 long and slender, 2 to 4 cm. long, 1 to 3 in 

 each areole; flowers yellow or purple; fruit 

 fleshy, smooth or tuberculate, scarlet or red- 

 dish. 

 Fruit small, about 1 cm. long, a scarlet berry, 



smooth ; flowers small, yellow 9. 0. leptocaulis. 



Fruit larger, 2 cm. long, green, more or less 

 tinged with red, somewhat tuberculate; 



flowers dull greenish purple 10. 0. hleiniae. 



Stems stout, 2 cm. in diameter or more; plants more 

 or less arborescent when fully grown, 3 me- 

 ters high or more; spines short, 1 to 2 cm. 

 long, numerous in the areole; flowers bright 

 purple; fruit dry, tuberculate, yellow when 

 mature. 

 Spines 2 cm. long, 4 to 10 in the areole; tuber- 

 cles large and conspicuous; sheaths loose, 

 shining and white at the base, brown- 

 tipped, giving the stem a whitish tinge. .11. 0. arborescens. 

 Spines mostly less than 1 cm. long, 12 to 20 in 

 an areole; tubercles mostly not conspicu- 

 ous ; spines giving a decided pinkish tinge 



to the stems. . . 12. 0. spinosior. 



Joints flattened, becoming orbicular, obovate, or elliptic, several 

 times as wide as thick. 

 Fruit dry, not succulent; spines light-colored, numerous 

 (except in 0. sphaerocarpa); joints small; plants pros- 

 trate, spreading. 

 Spines 35 to 100 mm. long, very numerous, 5 to 8 large 



ones in each areole 13. 0. hystridna. 



