DREER’S VEGETABLES UNDER GLASS. 51 
in the vicinity of Philadelphia, but is well suited to the needs 
of small gardeners and amateurs in this latitude. The large 
grower of to-day must have a forcing house, but the small 
grower can do well with a few sashes, getting the necessary 
heat from an underground bed of fermenting manure. For 
the preparation of hot beds the reader is referred to the 
chapter on that subject. 
The hot bed for lettuce culture can be made ready in the 
fall, or at any time during the winter. If lettuce is to be 
forced during the severe weather of January and February 
there must be a greater depth of manure employed in the 
construction of the bed than where it is made up in March 
simply for starting the seeds of bedding plants. 
A depth of two feet of manure is none too much for a 
mid-winter bed for forcing lettuce. A temperature of from 
50° to 65° is desirable ; and fresh air must be given in the 
day time, even in cold weather. 
Plants can be had from the out-of-doors seed bed, or 
from seedling plants in the cold frames. Such plants respond 
quickly to the genial bottom-heat of the hot bed, and are 
stimulated rather than stunted by the cool air which reaches 
them from above when the sashes are raised. 
The only reason market gardeners do not use hot beds 
is that they find a better economy in forcing houses; but 
the hot bed is well suited to amateurs or small gardeners, as 
already stated, and the bed can be employed for a second 
crop of lettuce if worked to good advantage. That is, it is 
possible to take well-grown plants from the seed beds (or, 
preferably, once transplanted), and quickly force them into 
head in a winter hot bed. Then, by having other well-grown 
plants available, a second crop can be brought forward in the 
same bed before it has lost all of its bottom heat. 
Forcinc Hovusz CuLture. The forcing house plan is 
simply the hot bed system developed on broad lines, but it has 
