CULTURAL DIRECTIONS 
443 
large enough for steam, provided the lines are not more 
than Go feet in length. The lines of pipe should be care- 
fully graded and have a uniform fall toward the return 
end; in fact, the rules governing greenhouse heating ap- 
ply to the piping of beds of this kind. A general idea 
of the construction of a pipe-heated bed may be gained 
from the cross section shown as Figure 102. 
In the far South it is not necessary to provide any 
kind of protection to the seed bed. I11 the North, pro- 
tection with glass or canvas will serve the purpose with- 
out artificial heating. 
Any fine, light, sandy soil may be used for bedding 
the potatoes. First, there should be several inches of 
soil in the bed and the upper inch free from all coarse 
materials. Then the tubers are placed, by hand, on the 
surface of the bed so that they do not touch each other. 
Very large potatoes may be split lengthwise, the cut sur- 
faces being placed next to the sand. After placing 
tubers, cover them with about 3 inches of fine soil and 
then water thoroughly. 
At the time of bedding the temperature of the bed 
should range from 80 to 85 degrees and be gradually 
dropped during a period of six weeks, perhaps, to 
about 60 degrees, when the plants may be set in the field 
if weather conditions are suitable. The air temperature 
