year’s buds. The American plane tree is the largest tree of the 
Eastern States. The street trees are usually the oriental plane 
tree, with yellowish under bark, and two or three fruit balls 
hanging together. The American, or occidental, plane tree has 
the under bark more nearly white, with the fruits usually sus- 
pended singly. 
Horse-chestmit . — The horse-chestnut is an Asiatic tree com- 
monly planted in cities because of its regular form and showy 
flower-clusters. The petals are usually white, spotted with purple 
and yellow. Only a few of the flowers develop into fruits, which 
are leathery, prickled burs, enclosing one or two seeds or nuts. 
The leaves are opposite, palmately compound, with five to seven 
leaflets. The buckeyes are American trees very similar; some of 
them have the fruits smooth when mature. 
Poplar .— The poplars bear their flowers in two kinds of cat- 
kins, staminate and pistillate. These grow on separate trees — 
that is, they are dioecious. The staminate catkins usually open 
earlier, being at first brown and later yellow with pollen. The 
pistillate flowers mature into small bottle-shaped fruits; these 
open later to let out the downy seeds. Poplars are wind pollin- 
ated. The Lombardy poplar is readily known by its tall, cylin- 
drical form. The cottonwood is the largest of the poplars; it is 
commonly planted where rapid growth is desired. The trembling 
poplar, or aspen, and the large-toothed poplar are common in the 
woods. 
Willow . — The willows grow mostly in damp places, and have 
a soft wood. They have usually slender yellow twigs and narrow 
leaves with stripules. The flowers are very much like those of 
the poplar, but are fragrant and pollinated by insects. The 
species are rather difficult to distinguish, since there are many 
hybrid forms. The w'eeping willow is an Asiatic species, often 
planted for its ornamental effect. The weeping effect results 
from the failure of the branches to develop sufficient mechanical 
tissue to hold them erect. 
Oak . — Oak leaves are simple pinnate, with a more or less wavy 
or lobed margin. The numerous species of oak fall into two 
groups that are readily distinguished. The w r hite oak group has 
round-lobed leaves; the acorns mature in one season; the bark is 
whitish and flaky. The black oak group has pointed-lobed leaves; 
the acorns mature in tw r o seasons; the bark is dark. The oaks 
are monoecious. The staminate flow’ers form long, drooping cat- 
kins. The pistillate flowers grow in clusters and develop into 
acorns. 
