262 BOTANY. 
parts of that district and generally known there as ‘“‘yellow pine”. A most 
variable tree, several forms of which have received distinct specific appel- 
lations, but the specimens collected in these expeditions all appear to 
belong to the ordinary smaller-leaved and smaller-fruited form. Whenever 
the macroscopic characters leave any doubt, the microscopic structure of 
the leaf appears to offer a sure guide. The leaves contain two or three or 
often more parenchymatous resin-ducts, usually of uncommonly small diame- 
ter, always with some, and often surrounded by many, of those strengthening 
cells of which I have spoken before; the same cells occur within the sheath, 
above and below the bundles of vessels. I have examined the leaves of 
20-30 specimens from the whole range of the species, and have never failed 
to discover this same structure, which I must therefore consider as char- 
acteristic of the species. 
Pinus Curmuanuana, Engelm. in Wislizen. Mem. note 26; Parlat. 7. ¢. 
397.—A middle-sized tree, with ternate, closely serrulate leaves 24-4’ 
long; the loose glistening sheaths 4’ long, deciduous after the first season; 
staminate flowers slender, cylindric, about 4’ long, sometimes interspersed 
among the foliage; involucre as long as the nearly entire-margined bract, 
of 8-10 scales, the outer about half as long as the inner ones; anthers with 
an almost orbicular crest; oval cones sub-terminal, small, 14’ long; knobs 
of the scales bearing recurved, deciduous prickles. 
Southern Arizona, in Sanoita Valley, at 6,500 feet altitude, Rothrock 
(649), in 1874; also Wright, and in Western Chihuahua, Wislizenus.—A 
tree 30-50° high, “with bark resembling yellow pine”; easily distinguished 
by the characters given, and especially by its deciduous sheaths. All the 
Strobi and Cembroids have such deciduous sheaths, but among the Pinas- 
ters the sheaths are persistent, except in one or two Mexican species, in P. 
Bungeana, above mentioned, and in this species. Leaves strongly and 
closely serrulate, and with three or often four parenchymatous ducts. 
Pinus contorta, Dougl., var LATIFOLIA, Engelm.; P. Murrayana, Balf. 
Oreg. Com. Rep.—A middle-sized tree, sometimes 60-80° high, and 2-4° 
in diameter, with thin, scaly bark of grayish to red-brown. color, and close, 
white, rather soft wood; leaves in pairs, 13-2" or rarely 3’ long and 1’ 
wide; staminate flowers oblong, 6’ in length, their involucre commonly of 
