438 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Joints large, 10 cm. long or more, nearly cylindric, 
3 to 4 cm. in diameter (strongly tuberculate); 
spines 3 to 5 cm. long, yellowish brown (flat- 
tened, stout)...............2.2.-020--20-0-- 4. O. 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. O. grahami. 
Spines shorter, 2 cm. long or less, one stout and , 
flattened, white, strongly recurved........ 6. O. 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. O. whipplei. 
Sheaths yellowish brown; plant of eastern New 
Mexico and Texas..................0.20000 8. O. davisii. 
Plants taller, branching from a simple or divided main 
stem, 1 to 3 meters high or more; flowers mostly 
purple, yellow in O. leptocaulis. 
Stems slender, 1 cm. in diameter or Jess; 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. O. leptocaulis. 
Fruit larger, 2 cm. long, green, more or less 
tinged with red, somewhat tuberculate; 
flowers dull greenish purple............. 10. O. kleiniae. 
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. O. 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..............2...2-.2.22.. 12. O. spinostor. 
Joints flattened, becoming orbicular, obovate, or elliptic, several 
times as wide as thick. 
Fruit dry, not succulent; spines light-colored, numerous 
(except in O. sphaerocarpa); joints small; plants pros- 
trate, spreading. 
Spines 35 to 100 mm. long, very numerous, 5 to 8 large 
ones in each areole................222-202eeeeeee 13. O. hystrictna. 
