PECULIARITIES OF PLANTS. 
227 
infested. The soil that appears to suit the plant completely is the black bog-earth 
of a true peat or turbary (not heath-mould), mellowed by long exposure and turn- 
ing to the atmosphere. Still, though prevention and remedial operations may be 
successful, we again urge the propriety to reject any plant, from small collections, 
which may be justly considered susceptible of disease or attack. 
The common green-fly (aphis) is an exception, because the remedy by fumiga- 
tion is comparatively facile, and its application, as respects the carbonaceous matter 
dispersed throughout the house, is rather beneficial than otherwise. 
Enough has been said of an infliction which fortunately does not frequently fall 
upon the plants under glass ; but let it alight where it will, whether on living sub- 
jects or on others deprived of life in the ordinary acceptation of the word, the bulk 
and analogy of facts seem to prove that every parasitic fungus is an educt from vege- 
table tissue, diseased, or brought at least into an altered condition, either by accident 
or by the operation of natural agents at a particular season. The decline of the year, 
when vegetable vitality is at the ebb, is the period when such fungi usually abound. 
We now are arrived at that part of our proposed object which will be most 
directly useful to the greater number of our practical readers. Plants, in common 
with animals, are very liable to diseases. Bad treatment, incompatible soil, and 
other circumstances not consistent with their natural habit, may and do bring on an 
unhealthy condition ; one which by the undue application of water, for instance, is 
frequently indicated by a sickly yellow tinge of the leaves ; but independent of erro- 
neous treatment, the natural health becomes affected, the colour fades, growth, if it 
do not wholly cease, is weak and spindly, and the plant perishes. 
As causes are not revealed, it were vain to allude to remedies ; it is then of 
moment to inquire what are those plants which are found upon general experience 
to be rarely susceptible of disease, or of injury from insects or mildew ; for it is cer- 
tain that a select collection of healthy subjects is much preferable to one of larger 
extent wherein malady and foulness are but too likely to occur. 
It is impossible to offer an opinion upon new and rare plants, which now are 
introduced by hundreds yearly ; but a notion of general habits may be pretty cor- 
rectly formed by observation of certain types. 
The whole tribe of Geraniums is in the early spring of some years exposed to the 
attack of an aphis ; this was proved to a perplexing extent, we believe in 1840, after 
a mild and wet winter. If neglected, the insects will run throughout a whole house 
with a degree of surprising rapidity ; but they may be destroyed by the fumigation 
already alluded to ; therefore the retention of this beautiful tribe must be indispens- 
able ; no greenhouse collection being complete without it. As however the Gerania 
approach to the nature of succulents, they rarely admit of intermixture with the hard- 
wooded, hair-rooted tribes. 
Such are the greater number of those very beautiful plants which rank among 
the " Heaths" (Ericea), and the " Epacris" (Ejjacridem) families. Fortunately, 
though requiring peculiar and refined treatment, they are little affected by malady 
