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** * Ascending: joints mostly smaller : spines few, slender, pliable, terete or scarcely angied, 
pale: berry smaller. 
7. O. tenuispina Eng. About 3 dm. high: joints rather large, obovate, attenuate 
at base, bright green, 7.5 to 15 cm. long, 5 to 10 em. wide: pulvilli somewhat approxi- 
mate, bearing short slender fulvous bristles, and mostly armed with 1 or 2 elongated 
(3.5 to 6.5 cm.) white spines, and 1 to4 shorter lower ones: flowers yellow, 6.5 to7.5cem. 
in diameter, with obovate retuse petals and clavate ovary: berry oblong, deeply um- 
bilicate.—Sand hills near El Paso. 
8. O. filipendula Eng. Plant 1.5to03dm. high, glaucous: roots long and knotted: 
joints orbicular or obovate or oblanceolate, thin, 3.5 to 7.5 em.long, 2.5 to 5 em. 
wide: pulvilli approximate, bearing numerous slender greenish-yellow bristles, 
armed or unarmed; the spines, when present, 1 or 2 elongated (2.5 to 5 cm.) ones 
with 1 or 2 smaller ones: flowers purplish, 6.5 cm. in diameter, with slender ovary.— 
Alluvial bottoms from the Pecos to El Paso. ‘‘The long knotted roots, small bluish 
joints, very small leaves, very long bristles, and purple flowers distingnish this 
species from all others” (Engelmann). 
** * * Procumbent or ascending : joints mostly smaller: spines stout, subterete or none, 
white or dark: berry clavate. 
9. O. Rafinesquii Eng. Diffuse and with fibrous root: joints obovate or suborbic- 
ular, very green, 7.5 to 12.5 cm. long, with elongated spreading leaves (6 to 8 mm. 
long): pulvilli somewhat remote, bearing slender reddish-brown bristles, mostly un- 
armed ; spines (when present) few, marginal, stout, straight, a single erect or spread- 
ing one 18 to 24 mm. long, and 1 or2 smaller deflexed ones, variegated reddish-brown: 
flowers yellow, often with a red center, 6.5 to 3.5 cm. in diameter.—A common species 
of the plains, and probably extending into the northern border of Texas. The follow- 
ing varieties, sometimes considered distinct species, are more southern and properly 
belong to the Texan flora: Var. GRANDIFLORA Eng. Somewhat ascending, with larger 
joints (often 12.5 to 15 cm. long), remote pulvilli (nearly 2.5 cm, apart), very slender 
bristles, mostly no spines, large flowers (10 to 12.5 em. in diameter) red in the center 
and with about 10 very broad petals, 5 stigmas, and an elongated-clavate berry.—On 
the Brazos.—Var. CYMOCHILA Eng. Diffuse, with orbicular joints (6.5 to 7.5 em. in 
diameter), less reinote pulvilli bearing straw-colored or fulvous bristles and mostly 
armed with 1 to 3 stouter spines (2.5 to5em. long) which are white with fulvous 
base and spreading or deflexed and often 2 or 3 additional smaller ones, 8 stigmas, 
and an obovate berry.—On the Llano Estacado.—Var. MACRORHIZA Eng. Prostrate, 
often ascending, with tuberous roots, obovate-orbicular very green joints (6.5 to 8.5 
em. long), somewhat remote pulvilli bearing reddish-brown bristles and only the 
upper armed, single stout often variegated spreading spines with 1 or 2 more slender 
deflexed additional ones, about 8 sulphur yellow petals reddish at base, 5 stigmas, 
and an obovate green or pale-ptrple berry clavate at base and broadly umbilicate,— 
Sterile rocky places between the Colorado and the San Antonio, especially on the 
upper Guadalupe. 
10. O. fusco-atra Eng. Diffuse: joints orbiculate-ovate, tuberculate, 6.5 to 7.5 em. 
long: pulvilli somewhat remote, large, grayish-tomentose, only the lower armed ; 
bristles numerous, stout, rather long (4 to 6 mm.), grayish-brown; spines usuaily a 
single stout brownish-black suberect one (2.5 to 3 cm. long) and often another shorter 
deflexed one: flowers yellow, nearly 7.5 cm. in diameter, with a conical ovary bear- 
ing pulvilli covered with long grayish-brown wool,—Sterile places in prairies west 
of Houston. ‘The stout brown, or above almost black spines, and the thick bunches 
of unusually stout brown bristles on the small joints, give this plant a very distinct 
appearance ” (Lngelmann). 
** * * * Prect or procumbent: joints pubescent: leaves minute: mostly no spines. 
11. O. rufida Eng. Erect-spreading, 6 to 12 dm. high, much branched: joints 
broadly obovate or suborbicular, 7.5 to 15 em. Jong: leaves long acuminate, 5 mm. 
