AN ENCYCLOPADIA 
OF HORTICULTURE. 199 
POPULUS (the ancient Latin name = palpulus, akin 
to palpitare, to tremble; probably so called from its 
trembling leaves). Poplar. ORD. Salicinee. A well- 
known genus of hardy, deciduous trees, with terete or 
angular branchlets, and having scaly buds, covered with 
resin; eighteen species have been described, natives of 
Europe, Central or mountainous and Northern Asia, and 
North America, including Mexico. Catkins loose, appear- 
ing before the leaves, the males often pendulous; flowers 
of both sexes usually shortly pedicellate, the females some- 
times on an elongated pedicel, racemiform. Leaves alter- 
nate, sometimes on laterally compressed, tremulous petioles, 
usually broad, penniveined, and trinerved at the base, 
entire, toothed or lobed; stipules narrow, membranous, 
fugacious. Some of the Poplars are amongst the most 
rapid growers of all hardy forest-trees. They thrive under 
a variety of. conditions as regards soil, &c., but do best in 
damp situations, such as along watercourses, &c. All are 
readily increased from cuttings, [inserted in the open 
ground; soon after the leaves have fallen is the best 
time to do ‘this. The weeping forms are generally 
grafted on tall, straight stems of the common upright- 
growing ones. 
Fungi. Many kinds of Fungi live on dead branches 
and stems of Poplars, and a good many also on living 
parts; but the only one of the latter that is usually very 
noticeable in gardens is that known as Ezoascus aureus 
(Taphrina aurea). This Fungus produces very con- 
spicuous spots on the leaves of Populus nigra. These 
spots bulge on one surface, usually the upper, so as to 
appear almost hemispherical, and may be from jin. across 
up to a much larger size, when two or more fuse together. 
The spots are usually duller green above, bright golden- 
yellow below; but sometimes the yellow colour is on 
the upper surface. The microscope shows that the colour 
is due to a layer of rather long cells, fixed to the surface 
cells of the leaf by one end, but free in the rest of their 
length. Each is full of a large number of small, round 
cells or spores, which escape by bursting the wall of 
the containing cell. When abundant, this Fungus is very 
conspicuous from its colour, and is very hurtful to the 
young trees, which it chiefly affects. 
The best remedy is the removal and destruction of the 
leaves, or of the branches, and even the whole trees if 
much infested, as soon as the Fungus appears. Perhaps 
the application of solutions of potassium sulphide or 
potassium permanganate might destroy the Fungus. 
Insect Pests. Poplars are liable to the ravages of a con- 
siderable variety of insects, mostly beetles and moths. A 
number of them are described elsewhere, and these species 
are merely mentioned here, the reader being referred 
to the fuller information given under the headings quoted. 
The wood of the trunks is bored into by the Poplar 
Fie. 251. POPLAR HORNET CLEARWING MOTH (Sesia 
: : : ~- apiformis). — : 
Hornet Clearwing Moth (Sesia apiformis, see Fig. 251), 
the larve of which live for about two years in the trees. 
See Sesia. The larvæ of the Goat Moth (which see) 
- are even more destructive. The young branches and 
Populus—continued. 
of the genus Saperda. The insects are rather slender, 
and nearly cylindrical, and of the general form shown in 
Fig. 252. 8. carcharias is about fin. to 14in. long, 
dusky-black, with grey or yellow pubescence, and rather 
long antenne ringed with grey and black; the wing- 
.cases are narrowed towards the tips. S. populnea is 
about šin. long, black, slightly hairy, and marked with 
pits over the surface; the thorax bears three yellowish 
lines; the wing-cases are not narrower behind; they 
are covered with a yellowish pile, and bear three or 
four large, yellowish spots; the antennm are ringed with 
ashy-grey and black. The larve of this species live in 
Fig. 252. A, SAPERDA POPULNEA, natural size; B, BRANCH OF 
PLAR, showing ravages committed by it. 
gall-like swellings in the branches (see Fig. 252) of 
Poplars and of Willows. There are a few other species 
of Saperda, but they do not call for special mention. 
Branches tenanted by the larvæ (shown by their galled _ 
| or withered state) should be cnt off; this is usually suffi- 
cient to kill the larve, but it is well to have the branches 
burned. — 
The leaves are devoured by several beetles of the 
family Chrysomelide—the leaf-eating beetles par excel- 
lence. Lina Populi is frequently very abundant on 
Poplars. This beetle is nearly ŝin. long, oval, and 
shining blue-black; the wing-cases red, except a black © 
tip, and very finely pitted; feet, and tips of antennæ, 
black. The larve are shaped much like those of Cocci- | 
. 
nella (see Ladybird); the head, the hinder part of the — 
body, and the legs, are black ; the rest of the body is 
