68 MISSOURI BOTANICAL GARDEN. 
In speaking of Y. rupicola and what he called its 
variety rigida, Dr. Engelmann* refers to intermediate 
specimens collected by Wright in «* Eastern New Mexico” 
(no. 1909). The leaves of this number in the Torrey 
herbarium ( Plate 37), it is true, are very hard to distinguish 
from narrower herbarium leaves of Y. rigida, but the cor- 
responding sheet in the Gray herbarium (Plate 38) clearly 
represents a crown of the acaulescent Y. rupicola with 
inner leaves, — narrower and less twisted than the outer 
leaves probably were. A similar intermediate specimen in 
the Engelmann herbarium, collected by Wright in April or 
May 1850, on “ Hills of the Blanco ”’ is from the region of 
and accompanied by unmistakable, though detached, leaves 
of Y. rupicola, to which I should refer all of these speci- 
mens. 
22. Capsule attenuate-beaked, with round-backed valves. 
Y. rostrata Engelmann, in herb. 
Of the aspect of Y. radiosa. Caulescent, at length 3m. high, simple 
or short-branched at the crown. Leaves very numerous, rigidly diver- 
gent, scarcely 10 mm. wide, a little glaucous, flat or biconvex, striate, 
thin, very pungent, the yellow margin minutely denticulate. Inflores- 
cence ample, with subincluded base or mostly exserted, glabrous. Flowers 
white, umbonate at base: style white, attenuate. Capsule oblong-ovoid, 
thick-walled, with convex valves long-attenuate and spreading above: 
seeds rather dull, 4 to 5X 6 to 7 mm. — Plates 36, f. 2. 40-42. 84, f. 3. 
Northern Mexico, from northern Chihuahua to the 
Sabinas valley in eastern Coahuila. — Plate 93, f. 2. 
In 1852, Dr. Bigelow, of the boundary survey, collected 
a Yucca with narrow denticulate leaves, somewhat resem- 
bling Y. rigida, at Bufatillo, said to be in a volcanic moun- 
tainous region near Presidio del Norte, and what may pos- 
sibly have been the same thing on sand hills thirty miles 
below San Elizario, — both along the Rio Grande, — and 
on gravelly hills at Los Moros. In August, 1880, Dr. 
Edward Palmer collected leaves, capsules, and seeds of ap- 
* Trans. Acad Sci. St. Louis. 3 50. 
