AN ENCYCLOPADIA 
OF HORTICULTURE. 171 
Plusia—continued. 
the silvery y. The hind wings have a broad, dark band 
along the margin, and the basal space is pale grey. 
The eggs are laid on the lower surface of the leaves. 
The larve are thickest at the twelfth segment, tapering 
forwards. They are bright green, with bluish-green 
dorsal liné, bordered along each side with a white line; 
and there are four more narrow white lines and a yellow 
line on each side, near the spiracles or breathing pores. 
There are a good many scattered, fine bristles on the 
body. The larvz rest with the-back arched, and move 
by looping. They feed upon all kinds of herbs, including 
Fig. 208. PLUSIA GAMMA, 
Nettles and other weeds, as well as upon many low culti- 
vated plants, such as Cabbages, Beets, Peas, Beans, &c. 
The best methods of effectively lessening their numbers are 
to destroy the larvæ, either by hand-picking, or by sweep- 
ing them, or beating them, off their food, and destroying 
them at once; or ducks and hens may be turned in to 
feed on them. Dusting the plants with soot or caustic 
lime is also recommended, though not very safe for 
delicate plants. Among the points to be specially attended 
to is the removal of weeds from gardens and field crops 
alike, as they afford shelter for the insects. 
PLUTELLA CRUCIFERARUM. A small moth, 
known also as the Diamond-back or Turnip-moth, belong- 
ing to the group of Tineina. It is excessively common 
throughout Great Britain; and, despite its small size, 
the ravages committed by the larve in some years are 
sufficient to force it on the notice of every observant 
farmer and gardener: The wings are about in. across. 
They are narrow, with long fringes, and are of a greyish- 
brown colour, with darker spots, the inner margin 
bearing a long, pale ochreous streak, with three prolonga- 
tions into the dark part. While at rest, the moths sit 
in a very characteristic attitude, with the antennx held 
straight forward, and nearly touching their support, and 
the wings folded over the body, like the sloping sides 
of a roof. The pale edges are thus in contact, and re- 
semble a row of three diamond-shaped spots. The legs 
are nearly hidden by the wings in the sitting insect. 
The larvæ are pale green in colour, with a darker head, 
several black dots on the next segment, and two yellowish 
spots on each of the next two segments. They have a 
few bristly hairs on the body, which tapers a little 
towards each end. They feed on the lower surface of 
the leaves of Turnip, Cabbage, and other Crucifere, 
eating away the substance of the leaf between the veins. 
Frequently, a dozen or more may be found on a leaf, 
and, w very numerous, or while the plants are small, 
the crop is apt to suffer severelyn.. When full-fed, the 
larve spin slight cocoons in the hollows between the 
leaf-veins on the lower surface, or on the soil, among 
rubbish, and change into pale brown pupæ, marked with 
black lines on the back and wing-cases. The moths 
emerge in from two to three weeks. There are two chief 
broods in the year, the moths appearing in May and 
August, and - larve about a month or six weeks later. 
Remedies. These are very difficult of application, since 
the larve live protected by the leaves from the direct 
application of insecticides, while their numbers and small 
Plutella Cruciferarum—continued. 
size render hand-picking slow, and unlikely to be suc- 
cessful, except on a small scale. The removal and de- 
struction of leaves, with numerous larva and pupe on 
them, and also of surface rubbish in autumn, lessens the 
risk to future crops. Brushing below the plants with 
branches of Firs, or of other twiggy shrubs or trees, has 
been recommended as likely to remove a number of the 
larve. Whatever favours rapid growth in the plants, 
e.g., manures and watering the plants in dry weather, 
will be of service; and gas lime and soot, thrown below 
the plants, might assist in keeping away the moths during 
the time of egg-laying, and in reducing the injury to 
the leaves. 
PNEUMONANTHE. Included under Gentiana. 
POA (from poa, an ancient Greek name for grass or 
fodder). Meadow Grass. ORD. Gramineew. A large genus 
(about eighty species) of hardy, sometimes dwarf annual, 
sometimes taller and perennial, grasses, broadly dispersed, 
but mostly found in North temperate regions. Inflorescence 
either in spreading or close panicles, the spikelets, for 
the most part, several-flowered and awnless; outer glumes 
unequal, and generally keeled; upper pales shorter and 
narrower, with inflexed, membranous margins. Few of the 
species: are grown in gardens, being mostly of agricul- 
tural value. Hight are British plants. The following are 
probably as much worth growing as any. They are of 
very easy culture in ordinary garden soil. Propagated 
by seeds, or by divisions. t 
P. fertilis (fertile). A synonym of P. palustris. 
P, — loving). fl., —— in : 
P. trivialis albo-vittata (common white-striped).* A very ele- 
gant, dwarf, perennial grass, forming dense t of erect leaves, 
which are flat, and broadly margined with pure white. Th 
a variety ofa hardy species, it is most effective, and proves, in 
t to its f to be a very useful decorative Plast, when 
grown in pots, under glass. A. 6in. 1868. (F. d. 5. 1 
POARCHON. A synonym of Trimezia (which 
see). 
POCOCKIA. 
see). 
Included under Trigonella (which 
POCULIFORM. Resembling a drinking-cup or 
goblet in shape. 
POD. A several-seeded, dehiscent, dry fruit. The 
Fig. 209. THREE-VALVED Pop OF Yucca. 
term is more — gle’ 1o = ee o Aa 
ee Tue Jeen ae: ae 
