Ss 
fe 1a | 
45 
or without smaller ones, which never occurs in any form of O. Mis- 
souriensis, where a large number of small setaceous spines is found, 
whether larger ones are present or not. Fruit 9 lines in diameter, with 
a small flat umbilicus. Seeds 23 lines in diameter. 
* « Articuli tumidi ovati. 
25. O. ertnacea, E. & B. |. c.: adscendens; articulis ovatis seu 
teretiusculis ; pulvillis confertissimis omnibus armatis ; aculeis 5-10 
gracilibus rubellis, 3-5 elongatis ; bacca ovata aculeolata ; seminibus 
magnis subregularibus. 
Near the Mojave, between the Colorado and the Californian moun- 
tains. — Joints 2-24 inches long, 1 — 1} broad, and $— 32 thick, some- 
times almost cylindrical, densely covered with large white pulvilli, 
which are only 2-3 lines apart. Spines 6-14 or even 20 lines 
long, slender but stiff. Fruit an inch or more in length. Seeds 
nearly 3 lines in diameter. 
26. O. arenarra, E. in B. C. R.: adscendens; articulis obovatis 
compressis seu teretiusculis tuberculatis ; foliis minutis; pulvillis sub- 
confertis pallide setosis; aculeis 1-4 robustioribus albidis fuscatis- 
ve, cum inferioribus brevioribus 2—6 albis; floris sulphurei ovario 
obovato ; petalis emarginatis ; stigmatibus 5; bacca oblonga spinulo- 
sa; umbilico infundibuliformi ; seminibus magnis irregularibus. 
Sandy bottoms of the Rio Grande near El Paso: fl. May.— 
Spreading 2-3 feet, }-—1 foot high; roots stout, creeping horizon- 
tally ; joints 14-3 inches long, 1-2 inches wide, and 3 ~- 3 thick, 
more strongly tuberculated than the allied species ; leaves only a line 
long; pulvilli 3-5 lines apart, very bristly, especially on the old 
joints; upper spines 9-15 lines long. Flower 2-23 inches in di- 
ameter. Fruit about an inch long. Seeds 24-8 lines in diameter. 
This is the only one of our Cactacee on which the Cochenille has 
been found. 
27. O. rracinis, Haw. (Cactus fragilis, Nutt.) : subdecumbens ; 
articulis parvis ovatis subcompressis tumidis vel subglobosis vix tu- 
berculatis nitide viridibus ; foliis minutis ; pulvillis subconfertis magnis 
albo-tomentosis, vix setulosis; aculeorum 1-4 robustiorum summo 
valido angulato fuscato porrecto, ceteris debilioribus pallidioribus pa- 
tulis seu radiantibus; aculeis inferioribus 2-6 gracilibus albis radi- 
antibus ; floribus minoribus ; bacca ovata vix spinulosa, umbilico in- 
- fundibuliformi; seminibus paucis magnis subregularibus. 
