54 
WAYSIDE AND WOODLAND TREES. 
The Poplars {Popnlus). 
Almost everybody who has an elementary acquaintance with 
trees knows a Poplar at sight, the foliage being so very distinct 
from that of other trees. But the distinctions between the 
several species are not so immediately obvious. Five kinds 
of Poplar are commonly grown in this country, of which only 
two are regarded as distinct indigenous species. These are 
the White Poplar {Populus alba), and the Aspen {P. iremuld). 
A third indigenous form, the Grey Poplar {P. canescens), is 
thought to be either a sub-species of P. alba, or a hybrid between 
that species and P. tre7nnla. Then of common introduced 
species we have the Black Poplar {Popuhis ?tigra), and the 
Lombardy Poplar {P. fastigiatd). 
The Poplars (Populus) and the Willows (Sallx) together 
constitute the Natural Order Salicinece. The two genera 
agree broadly in the construction and arrangement of their 
flowers in catkins, but whereas the Poplars have broad leaves 
and drooping catkins, the Willows, with few exceptions, have 
long slender leaves and erect catkins. The sexes are not 
only in distinct flowers, but on separate trees — what botanists 
describe by the term diascious. The males appear to be far 
more numerous than the females. In the popular sense there 
are no flowers, for there are neither sepals nor petals, each 
set of sexual organs being protected merely by a scale. The 
catkins containing these flowers usually appear before the 
leaves. As there is nothing to attract insects to the work, 
the trees have to rely upon the wind for conveying the pollen 
to the female trees. The first three species described below 
have from four to twelve stamens ; P. nigra and P. fastigiata 
have from twelve to twenty stamens. The Poplars share the 
love of the Willows for moist places. They are found more 
frequently in gardens and hedgerows than in woods. Their 
