132 
ON MANURE, 
of a particular species, by employing a quantity of earth (such as the plant deliglii 
in), in the different crannies and crevices; and, as in the case of various terrestrif 
orchidacese, which naturally choose limestone in preference to any other stond 
wherever any partiality is displayed, it should be humoured, observing only, ths' 
but one description of rock shall meet the eye. Thus chips of Bath stone, c 
common sandstone, which imbibe a considerable quantity of moisture, and pai 
wdth it slowly, forming a reservoir from which an even and constant amount d 
moisture is supplied, may be used with advantage in places not exposed to view 
and indeed any porous stone, though differing from that principally employed, man 
be used beneath the surface. Rough arms of decayed wood may appear here an 
there for epiphytal orchidaceae, without impropriety. Hence, whilst the ey 
observes nothing unnatural or inconsistent in the groundwork, all the varie 
vegetation that clothes it, may severally meet with their peculiar wants. 
It must be evident that on the irregular, convex, or sloping surface of rocken 
there will be room for a greater number of plants than can be cultivated on a fit'* 
surface. We would therefore suggest for large conservatories that, independent (i 
the main rock work, at least a portion of the borders should be raised in the middk 
and partly covered with rock ; upon which, beneath the partial shade of tallJ 
plants, ferns and a few rapid-growing trailing things might be planted. '' 
As large houses are likely soon to become much more frequent than they ha\ 
hitherto been, greater facilities will be opened for the formation of glass-houi 
rockeries. We therefore leave the subject for the present, in the hope that tl 
propriety and ornamental advancement of cultivating tender exotics on rockworls 
will be more fully appreciated and practically adopted. ^ 
ON MANURE. 
We have been in the habit of considering as manure every decomposable | 
putrescent material which exists naturally in, or is artificially added to, the eartlij| 
Thus, the fibrous masses left in the ground, green vegetable subtances chopped j. 
pieces and dug in, and the black vegetable portions of heath or moor-soil are 
reality, manures. Earths proper, namely — alumine and clay, silex or sand, chal] 
phosphate of lime, and metallic oxides are themselves almost insoluble ; and cs 
act only, or chiefly, as the bed, or fundamental support, of plants : or, to spe^ 
more philosophically, — the laboratory — wherein the interchange between t| 
laborated products of decomposition and the roots of the plant is carried on. Thej 
general truths are equally applicable to garden and pot-culture — there is ij 
distinction so far, between the processes of the florist, the amateur, the nurserj, 
man, and market-gardener-— all are included therein. | 
Our present remarks will not apply to solid manures ; the subject which clair 
