THE PHILOSOPHY AND USES OF BOTTOM-HEAT. 
159 
appropriate way of assisting their spring and summer growth ; and, according to 
our long-since declared views, the spring and summer constitute the time at whicli 
alone plants require artificial stimulation. 
Although so few cultivators evince a consciousness of the advantages of bottom- 
heat, on a large scale, it is easy to show that all acknowledge its value in some 
instances. In propagation, for example, cuttings or seeds of plants from warm 
climates are very rarely put in without being plunged in a bed that is heated 
from below. Gloxinias, Gesneras, Achimenes, and other fast-growing plants, are, 
moreover, seldom cultivated in a stove that is not furnished with bottom-heat. 
And if the principle that bottom-heat facilitates superior growth, or the formation 
of roots, be thus universally subscribed to in a practical way, there can surely be 
no reasonable objections to the general carrying out of tliat principle, so as to include 
every kind of stove-plant. 
In respect to the fittest mode of creating bottom-heat, there will probably be a 
difi*erence of opinion among practical men, some preferring that produced by bark, 
as the cheapest, and others deeming that caused by a hot- water apparatus superior, 
because most easily regulated. Most unquestionably the bark-bed is the simplest ; 
but it requires occasional stirring and renewal, which may be inconvenient. 
Whichever method may be fixed upon, there should be a raised brick-pit for 
applying it ; — in the centre of the house, if it be a span-roofed erection, and forming 
the body of the house whether there be or be not a path at the back of the pit, in 
a structure with a lean-to roof. The height of this pit and of the paths must be 
determined by the height of the house, and the tallness of the plants intended to 
be grown. For plants of from one to three or four feet in height, the top of the 
pit should not be more than four and a half or five feet from the roof, and about 
three or four feet above the walk. Half a brick will be quite a sufficient thickness 
for the walls. 
If bark is to be used, the bottom of the pit should be filled, to the depth of two 
or three feet, with pieces of the rough branches or roots of trees, mixed with some 
rough stones, in order to form a thorough drainage. On these, the bark should be 
placed to the depth of a foot or eighteen inches, according to the size of the pots 
to be plunged ; and the actual depth of the pit will thus be four or five feet, for 
it should be filled a little above the surface-level, to allow for a little settling. 
When the heat of the new bark is somewhat subsided, and the whole is thoroughly 
settled, the plants may be plunged into it about half the depth of the pots, putting 
them in up to the rim after the temperature has been still further lowered. By 
the use of heat-sticks, the amount of heat may always be ascertained ; and on its 
falling away considerably, the plants can be taken out, and the bark turned over. 
Subsequently, the addition of a little fresh bark will be necessary at each stirring. 
Where heating by hot water is chosen, th^ pipes should be arranged in the 
lower part of the pit, and chambered in by thin slabs of stone or slate, which 
should be perforated to allow the heat to pass through them. A layer of gravel- 
