104 GREENHOUSE CONSTRUCTION AND HEATING. 
Cucumber houses should be fitted with brick -pits, 
3ft. or 4ft. wide, on each side (in the case of span- 
roofed structures), see Fig. 8, or along the front only if 
a lean-to or three-quarter span. An arrangement of 
this kind is absolutely necessary where winter and early 
spring crops are required, though plants for summer 
cropping are frequently grown in mounds of soil laid on 
an ordinary raised staging, or even on a solid bed of 
ashes, etc., and as long as the warm weather lasts they 
usually succeed fairly well in this way, though not so 
well as in brick beds, even without the bottom heat. To 
provide this, one or two rows of 4in. piping should be fixed 
along the bottom of each pit, surrounding them with 
brickbats, over which some turf sods or littery manure 
is placed, and then the soil. Except in very cold places one 
row of pipes is usually sufficient, and, indeed, better than 
more in most cases. This should be a flow, but if two 
rows are put in let them be flow and return, the former 
being placed outside. Without the gentle bottom heat 
thus afforded the plants do not* thrive in cold weather, 
though in the height of the summer it is unnecessary, and 
the fire may then be let out. 
Note that this method of surrounding the pipes with 
brickbats or clinkers, and covering this with some rough 
materal must not be employed in the construction of hot- 
beds for propagating purposes, ete. Beds thus constructed 
are invariably failures, as the heat does not penetrate 
through to the surface of the bed with sufficient freedom 
to do any good. For all such purposes there should be 
a false bottom, or diaphragm, of galvanized iron or some 
conducting material, with a hollow chamber beneath for 
