I • p*S. si. ?(, /K 0^1 
-2^/ ' 42 
, very vigorous specimens more patulous: spines, when present,less 
than 1 inch long, but stout. Flower about 2 inches in diameter, pale 
yellow. Seed 2| lines in diameter. It se^ms to be well distinguished 
from O. Rafinesquii (which grows only west of the Alleghanies) by the 
smaller size, paler color, small pul villi, usually the absence of spines, 
the smaller flower, with all the parts less numerous, and especially 
by the short, thick, and more or less appressed leaves. 
§ 5. Pubescentes: erect® seu procumbentes : articuli pubescentes: 
folia minuta : aculei subnulli. 
* Flavijlorce. 
19. O. microdasys, Lehm.: erecto-patula ; articulis oblongis obo- 
vatis seu orbiculatis pubescentibus laete viridibus ; foliis minutis ; pul¬ 
villis confertis inermibus lanam flavidam setasque numerosas gracilli- 
mas flavas gerentibus. 
Only south of the lower Rio Grande, near Rinconada, etc. — Plant 
2-4 feet high; joints 2-3 inches long, l|-2 wide; pul villi £--J 
of an inch apart. 
20. O. rufida, E. in B. C. R.: erecto-patula; articulis late-obovatis /[ 
seu suborbiculatis pubescentibus; foliis longe acuminatis; pulvillis 
confertis setas rufidas graciles numerosissimas gerentibus inermibus; 
floris flavi ovario obovato pulvillis numerosis instructo; stigmatibus 7 I 
in capitulum congestis. I 
Common about Presidio del Norte, on the Rio Grande : fl. May. — 
Stem 2 - 4 feet high, much branched ; joints 3-6 inches long ; leaves 
2| lines long. Flower 2J inches in diameter, with 40-50 pulvilli on 
the ovarium. — Apparently near O. microdasys and O. puberula ; flis- j I 
tinguished from the former by the rounded joints, larger leaves, and .SI 
red-brown bristles; from the latter by the entire absence of spines, 
and of the purplish spot which in that species surrounds the pulvillus. . 
Further investigations are necessary to decide about these closely 
allied forms, as about most species of this intricate genus. 
# # Rubriflorce. 
21. O. basilaris, E. &. B. 1. c.: humilis; articulis obovatis seu 
triangularibus glaucescentibus pubescentibus e basi proliferis; foliis 
minutis; pulvillis subconfertis fulvo-villosis setas gracillimas demum 
numerosissimas fulvidas et subinde aculeolos setiformes caducos ge¬ 
rentibus; floris purpurei ovario obovato pulvillis plurimis instructo; 
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