CULTURAL DIRECTIONS 443 



large enough for steam, provided the lines are not more 

 than 60 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. 



FIG. IO2. CROSS-SECTION OF PIPE-HEATED FRAME 



In the far South it is not necessary to provide any 

 kind of protection to the seed bed. In 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 #bout 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 



