134 
LEAF-MOULD FOR EXOTICS. 
of exotics ; and it seems to have been forgotten that there is an unalterable 
tendency in small particles of earth to lie close to each other, and even to con- 
solidate, when brought into contact, thus either throwing off the water from their 
surface, or holding it too long in the mass. The sifting of soils, therefore, in order 
to use the finer portion, has been a great evil ; and the addition of sand, with the 
view of rendering them more porous, has rather augmented the mischief; for 
every one knows how difficult it is to get fluids to circulate among sand, when the 
latter is at all dry. Hence the more recent practice, educed from the known laws 
of nature, that the larger the particles of matter brought together, the greater will 
be their interspaces and general porosity, while they will become proportionately 
less liable to amalgamate, is to employ those earths, for plants in pots, which are 
made up of the coarsest, and lightest, and least adhesive ingredients, and to mix 
with them similar pieces of stone, potsherds, &c., to increase and maintain their 
porosity. 
If we might illustrate our meaning by a bold metaphor, we should say that all 
soil intended for potted exotics should be literally like a sieve, or a piece of 
canvass or netting, through which the water might flow as soon as it was poured 
on it ; only that each particle should absorb just enough to moisten it throughout. 
This we should consider the perfection of a soil, in relation to its mechanical 
properties ; and this is unquestionably indispensable to the attainment of the 
cultivator''s highest objects. 
Still, there are several barriers to the preparation of such a compost, on account 
of the necessity of providing for the plant's sustenance ; adequately rich earths 
being ordinarily somewhat adhesive. Loam, in its more nutritive state, is com- 
monly inclined to be clayey, or at least, rather too retentive of moisture, and 
disposed to adhere too much into a mass. When very light and open, again, it is 
often sandy and poor. Heath-mould, on the other hand, is sometimes so full of 
siliceous matter, and so free from vegetable fibre, that it is the worst of all earths 
for remaining porous, and will soon settle down into a sour ball, either impervious 
to water, or entirely saturated ; whereas, when it is nearly all fibre, and destitute 
of sand, thus constituting the most easily drained of soils, it will only suit those 
plants which require very little nourishment from the earth, such as Heaths and 
Orchidaceae. 
Taking all these matters into account, we have gained the conclusion that 
leaf-mould, used alone for some plants, and in conjunction with loam or heath-soil 
for others, offers so many advantages, that every person having a garden should 
save all the leaves they can command, and appropriate them specifically to the 
purposes of cultivation, particularly with plants that are grown in artificial 
circumstances. In the first place, it is so porous that we have never seen it bind 
into a mass ; and the pot must indeed be badly drained in which it holds an undue 
quantity of moisture. Secondly, it is much richer than heath-soil ; and contains 
just enough of nutriment to bring the majority of shrubby plants to a high degree 
