50 
the same habitat, viz.: in canons, near water, at the-same altitude, 
and in the same region. A mere form, or individual variation of 
the Black Cottonwood, it cannot be. Of the more than 100 trees 
growing in Carter Canon, I did not see a single one that had lanceo- 
late leaves with short petioles, nor a narrow crown; and at Little 
Elk, where I saw about as many trees of the true P. angustifolia, 
I did not notice a single one that had the long petioles and 
abrupt acumination characteristic of my No. 372. At Hot Springs, 
I saw only three Black Cottonwoods, and all three agreed with 
those from Carter Canon, except that the leaves were broader. 
Dr. Chas. E. Bessey and Prof. T. A. Williams, of South Dakota 
Agricultural College, who have both seen the Black Cottonwood 
several times have not seen a form like this. The fact that my No. 
372, in both places was growing together with P. monilifera, might 
suggest the possibility of its being a hybrid of that and P. angustifo- 
“a; but the total absence of the latter tends’to show the contrary. 
Believing that there are two American Black Cottonwoods, I 
shall try to give the distinguishing characters: 
Populus angustifolia, James.—Leaves lanceolate or ovate, grad- 
ually acuminate, with cuneate, rounded, or heart-shaped base, on 
short petioles (1% inch long), thickish, drying yellowish or brown- 
ish, finely crenate-serrate from base to apex; lateral nerves in the 
larger leaves often 10-15; crown narrowly pyramidal with ascend- 
ing branches. Collected by Dr. Chas. E. Bessey, at Manitou, 
Col., July 18, 1886, etc.; by T. A. Williams, in War Bonnet Canon, 
June, 1890, etc.; by myself, in Little Elk Canon. (Plate CXL.) 
Populus acuminata, n. sp. (No. 372 of my Nebraska Collec- 
tion). Leaves more or less rhomboidal, abruptly acuminate, with 
cuneate base and long petioles (1’—2’ long, or more), semi-pendent, 
thinner than in the preceding, drying green; denticulation scarcely 
any at the base and near the top; at the middle, regular and 
larger than in the preceding; lateral nerves seldom more than 8 
on each side; crown broadly pyramidal with spreading branches. 
Collected by me in Carter Canon, Scott’s Bluff Co., Neb., July 25, 
1891, and at Hot Springs, S. D. (Plate CXLI.) 
LuTHER ACADEMY, WAHOO, Ngs., Oct. 15, 1892. 
X 
[ Mr. Rydberg’s description of P. angustifolia and his figure (Plate CNL.) agree 
accurately with James’ type specimen, preserved in Herb, Torrey. N. L. B.] 
