18 VEGETABLE FORCING 
are also located conveniently to the boiler. Wide alleys 
(Fig. 5) lead from various parts of this mammoth range 
direct to the packing room. When the products are 
loaded on wagons there is probably no better arrange- 
ment than a low, central building which serves as a drive- 
way, packing shed, office and boiler room, with the green- 
houses running out from both sides. 
The greenhouses should not be shaded more than 
necessary by the central building. Asa general rule, very 
wide houses should be separate because they shade each 
other more than do narrow ones. In the East, where 
wide houses are most used, it is customary to leave a 
space of 12 to 16 feet between them. The fact cannot be 
disputed that wide, separate houses admit the most light, 
and for that reason they are best adapted to the winter 
culture of vegetables. Separate houses are well suited to 
regions where heavy snowfalls occur. Nevertheless, 
because they are more expensive to construct and to heat, 
they do not meet with favor in many séctions, ‘especially 
in the West. Separation causes inconvenience in the 
daily care of the crops. Compact, connected ranges 
(Fig. 6) are entirely satisfactory under most conditions, 
especially when lettuce is the main winter crop. Many 
growers prefer the even-span type of construction with 
connected houses 30 to 40 feet in width. (Fig. 7.) 
Forms of greenhouses.—There are three general forms 
or types of greenhouses, viz.: (1) Lean-to or half-span, 
(2) even-span, and (3) three-quarter span. Lean-to 
houses (Fig. 8) are generally built against the south side 
of walls or buildings. They were common in the early 
days of vegetable forcing. They are fairly satisfactory 
for the growing of a few vegetables for the home table, 
but should seldom be considered for the growing of crops 
on a large scale, for commercial purposes. They are in- 
expensive to erect and economical of fuel, but their limita- 
tions with regard to light and sunshine render them 
