70 
SILVA OF NORTH AMERICA. 
SALICACEZ. 
Populus acuminata is sometimes planted to shade the streets of Laramie, Denver, Colorado Springs, 
and other cities in the region which it inhabits.’ 
sium. He came to America in 1882, and from 1884 to 1890 and 
again from 1891 to 1893 was a teacher of natural sciences and 
mathematics at Luther Academy, Wahoo, Nebraska. The years 
1890-91 and 1893-95 he spent at the University of Nebraska, re- 
ceiving from that institution the degrees of Bachelor of Science in 
1891 and of Master of Arts in 1895. In 1895 Mr. Rydberg entered 
Columbia University and three years later obtained the degree of 
Doetor of Philosophy. From 1895 to 1896, while a student at Co- 
lumbia University, he performed the duties of Professor of Natural 
Sciences and Mathematics at the Upsala College in Brooklyn. 
During the summers of 1891, 1892, and 1893, he was a field agent 
of botany of the United States Department of Agriculture ; in 1895 
and 1896 of the Division of Agrostology of that Department, and 
in 1897 of the New York Botanic Garden, collecting plants in Ne- 
EXPLANATION 
Puare DCCXXXI. 
. A fruit, enlarged. 
ONAnkrwne 
braska, South Dakota, Wyoming, Colorado, Utah, and Montana. 
Mr. Rydberg is the author of a number of botanical papers and re- 
ports, including a Flora of the Black Hills of South Dakota and of 
the Sand Hills of Central Nebraska, a paper on the Grasses and 
Forage Plants of the Rocky Mountain Region, with Mr. C. L. Shear, 
a Monograph of the North American Species of Physalis and Related 
Genera, a Monograph of the North American Potentille, and a Cata- 
logue of the Flora of Montana and the Yellowstone National Park. 
1 The oldest specimen of Populus acuminata which I have seen 
was collected by Dr. F. V. Hayden on Reynolds’s expedition to the 
headwaters of the Missouri and Yellowstone rivers in 1859-60, 
and is preserved in the Engelmann herbarium. In 1874 it was col- 
lected by Engelmann at Denver, Colorado, and in 1880 I found it 
in the streets of Colorado Springs. 
OF THE PLATE. 
Populus ACUMINATA. 
. A branch with staminate flowers, natural size. 
. A staminate flower, enlarged. 
. The bract of a staminate flower, enlarged. 
A branch with pistillate flowers, natural size. 
. A pistillate flower, enlarged. 
. A fruiting branch, natural size. 
A leafy branch, natural size. 
