246 WOODY PLANTS OF MASSACHUSETTS. 
more serious one is the liability of the branches, or even the 
trunk, when very tall, to be broken by the wind. Its particular 
office seems to be to act aS a screen and as a nurse to other 
more valuable trees while young. When this office is perform- 
ed, it may be felled, but is not easily eradicated, on account of 
the extreme vitality of the roots, which continue for years to 
throw up suckers. 
In favorable situations, in a moist, rich soil, this tree attains, 
in a comparatively short time, to a largesize. I have not found 
this tree growing naturally in Massachusetts or elsewhere. It 
is, however, more frequently planted for shade and ornament 
than any other tree of the genus. 
Sp. 4. Tue River Porrar. P. levigdia. Aiton. 
Leaves and a section of a branch figured by Michaux, under the name P. 
Canadensis, Sylva, II, Plate 95. 
The river poplar is a noble tree, rising often to the height of 
eighty feet or more, with a fine long open head. The trunk 1s 
of a light granite gray color, somewhat rough in old trees, with 
roundish ridges, separated by longitudinal furrows. ‘T’he young 
trees and the large branches of old trees are covered with a 
smooth leather-like bark. The smaller branches are of a light 
gray; they are often dependent from the lower limbs. The 
upper ones go out ata sharp angle, and tend upwards. The 
recent, vigorous branches and shoots are of a bright green color, 
like the leaves, with scattered, long, white, lenticellar dots, and 
strongly angled by three, brown, sharp ridges running down from 
the base and each side of the leafstalks. Older shoots are of a 
grayish green, with the ridges longer, more prominent, and of a 
darker color. The upper branches are conspicuously ridged, 
with the bark longitudinally cleft, the ridges frequently cracked 
across. Pith large, five-angled. 
The buds are long, and taper to along sharp point. The leaf- 
stalks are nearly as long as the leaves, and gradually and 
strongly compressed towards the leaf, at the base of which are 
often situated two or more conspicuous glands. The leaves are 
very broad ovate or heater-shaped, nearly as wide as long, being 
from three and a half to four and a half inches wide, and from 
