348 FORCING GARDEN 
that, where the stock of pine-plants is not extensive, cer- 
tain and abundant crops of fruit cannot be expected. In. 
stead, therefore, of a succession and fruiting-house of the 
old form, with two fires each, it would be better to have 
four pits with single fires. There might be two succession- 
pits of the forms represented, supra, pages 344, 345, and 
two fruiting-pits similar to the figures on page 346. These 
would contain a much greater number of plants than two 
pine-stoves, would be little more expensive in erection, and, 
as the number of fires is the same, would not consume 
much more fuel. 
Bottom-Heat.—As a substitute for the warmth absorbed 
by the earth from the powerful rays of the sun in tropical 
countries, the pots of pine-plants are generally plunged in 
a bed composed of tanners’ bark, decaying leaves, or other 
fermenting substances. Tanners’ bark is most commonly 
used. Speechly and Nicol prefer leaves shed by hardwood 
trees in autumn. Others form the under and greater part 
of the bed with stable-litter. Whatever substance is em- 
ployed, it should not be put into the bed until the first 
violent heat of fermentation have passed; or, if circum- 
stances impose a necessity of using it in a recent state, it 
should be largely mixed with old materials of the same 
kind. A layer of exhausted bark, ten or twelve inches 
thick, should be laid on the surface of the bed. In pine- 
stoves, the curb of the bark pit is usually elevated about 
three feet above the common level of the house, and has a 
gentle slope towards the front; in pine-pits, however, it 
approaches more closely to the glass. The bark is com- 
monly five or six feet deep; but it may be questioned 
whether this depth is not excessive and unnecessary. A 
bed about three and a half feet deep would probably-be 
