Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 4, Pt. 3

CAOTACE,E.
About Albuquerque, where Dr. Wislizenus had already collected it in 1846; apparently
extending into Mexico, as Dr. Gregg collected what seems to be the same species about Sau
Luis Potosi. Shrub 3-5 feet high; lower part of stem 1-11 inch thick, covered with scaly,
light-yellowish-brown bark; older branches smooth terete, younger ones 3-4 lines in diameter,
strongly tuberculated; tubercles 6-9 lines long; leaves slender, about 3 lines long, and apparently somewhat persistent, as they are sometimes found adhering, though withered, even to
fruit-bearing branches, which, of course, are over a year old. The same, though to a less extent,
is sometimes seen in 0. frutescens. Pulvilli unusually large; bristles in the young ones forming a small but distinct bunch at the upper edge of the areola, but disappearing on the older
joints, contrary to the usual occurrence, when the bristles become stouter and more numerous
in older joints. Spines 1-21 inches long, dark, with very loose and glistening sheaths; second
or smaller spine sometimes lateral, but usually above the principal one, not below it, as in most
others. Flower unknown. Fruit ovate, 8 or 9 lines long, the pulvilli often bear 2-5 obtuse
bodies, almost hidden in the tomentum, apparently glandular, but of a fibrous structure. Seeds,
12-15 in each fruit, about 2 lines or a little more in diameter, commissure broad, prominent,
forming a distinct, somewhat spongy, rim. (See plate XX, fig. 1, and plate XXIV, figs. 1315.) In Dr. Wislizenus' report, the long-spined form of 0. frutescens was confounded with this
species. It is possible, however, that 0. vaginata, as described here, may be a stouter, tuberculated form of 0. frutescens, with lighter colored, tuberculated fruit, and larger-seed.
27. 0. FRUTESCENS, Engelm. This well known species was observed from Laguna Colorado,
60 miles east of the Pecos, to Williams' river, a branch of the great Colorado, always with the
same characters. The bark is scaly, almost papery, with a silvery reflection; the wood shows
the medullary rays very distinctly, especially 5 of them; much less the annual layers. Fruit
deep scarlet, smooth, small, sometimes almost obliterated pulvilli, 5-9 lines long; seeds 5-10,
about 1~ lines in diameter, with a narrow and often acute margin. The forms collected on the
expedition belong to var. a. longispina; the var. P. brevispina has been observed only in Texas
and northeastern Mexico. (See Plate XX, fig. 2-5, and Plate XXIV; fig. 16-19.)
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