49 
lanceolate leaves, 2-5 inches. All the leaves are gradually acum- 
inate towards the apex, and finely crenate-serrate from base to 
tip. Inthe specimens collected by Dr. Bessey, at Manitou, Col., 
July 18, 1886, the first leaves are very broad, with rounded or 
even cordate base. In my own specimens from Little Elk Canon, 
S. D., June 28, 1892, the leaves are small and nearly all lanceolate. 
The leaves of my No. 372 differ, besides in the length of the 
petiole, in being rhomboidal, always having cuneate base and an 
abrupt acumination. The teeth are scarcely any from the base to 
near the broadest part of the leaf, from there they are more regular 
and larger than in P. angustifolia, till they disappear again at 
the acumination. The specimens from Carter Canon have the 
leaves twice as long as broad, and with long acumination. In 
those from Hot Springs the leaves are broader (the breadth 
equalling 24 or 34 of the length) with a shorter acumination. 
The latter are in form like the leaves of P. Hudsonica, Michx. f., 
figured in Silva Americana, but the shoots and petioles are 
not hairy. They also resemble those of the Black Cottonwood 
of Europe, P. nigra (P. Hudsonica, according to Gray), which, 
however, if I am not mistaken, has angled petioles. It seems to 
approach the true cottonwoods in several respects.* I have 
mentioned above the form of the leaves and the length of the pe- 
tioles. The old bark resembles somewhat that of P. monilifera, but 
is whiter. The crown, although pyramidal in form, is more exten- 
Sive than in P. angustifolia, the branches being more spreading 
and the leaves semi-pendent. Thetrees of P. angustifola that I 
have seen were all narrowly pyramidal with ascending branches, 
giving them the aspect of a willow, a fact, as is stated before, 
which then has been noticed by Dr. Bessey. 
What, is this cottonwood? Four alternatives present them- 
Selves to me: a species distinct from P. angustzfolia, a local variety, 
a mere form of the same, or a hybrid. As I have stated before, 
Iam most inclined to believe the first. A local variety, produced 
by the climate, it cannot very well be, as the two are growing in 
*In D.C. Prod., the American Black Cottonwood is referred to the Common 
Cottonwood, under the name Populus Canadensis, var. angustifolia, Wesmael. To 
place our 2 angustifolia as a variety of P. Canadensis (P. monilifera) was, indeed, : 
a blunder. If Wesmael had seen my No. 372, instead of the true 2 angustifolia, —— 
the mistake would be, perhaps, more excusable. ae 
es Pa me eee 
