350 PRINCIPLES OF BOTANY, ETC. 
species. Secondly, by the Coccus, of which there 
are various species. ‘That which in our hot-houses 
is mostly met with, the Coccus Hesperidum, is the 
most dangerous ; those which are commonly found 
on the roots of Scleranthus, Polygonum and others, 
are less noxious. ‘he disease is lastly produced by 
the Acarus ¢ellarius, a small mite, which in hot- 
houses likewise spins a very delicate web, over the 
leaves of the plants, and thus destroys them. Against 
the first species, careful cleaning or even brushing 
with suds, or a decoction of tobacco; or fumes of 
tobacco in close rooms, may be of service. The 
same means may be tried with advantage against the 
second species, where it may be likewise very bene- 
ficial to place the plant as soon as the temperature is 
mild in the open air, ina shady, but airy place. 
This last we use likewise to get rid of the Acarus, 
which in hot-houses chiefly attacks the genera Sida, 
Hibiscus, Dolichos and Phaseolus. 
§ 323. 
Verminatio, or worms, is not the same affection as 
in animals, for it is not worms which produce it, 
but the larva of.insects. Stem, leaves and fruits 
suffer more particularly from it. ‘The stem of some 
trees is very often eaten through, and often dies on 
this account. ‘The willow, (Salix a/ba); horse-ches- 
nut, (Aesculus bippocastanum) ; the- Typha /atifolia, 
may serve as instances. 
The leaves are often inhabited by the mining- 
worm, as it is called, especially the leaves of cher- 
ry-trees. 
Fruits, 
