Propagation 71 



" The wooden floor should be built at least four 

 inches above the flue, so as not to catch fire and to 

 give better distribution of heat. The floor should have 

 a slope of one inch to seven and one-half feet, or twelve 

 inches in ninety feet. That is, the soil at the furnace 

 end should be eighteen inches deep and at the chimney 

 end six inches deep. The flue under the floor should 

 have the same slope as the floor. The soil on top of the 

 frame should be level. Any kind of rough boards may 

 be used as flooring. They should be treated with creo- 

 sote to make them more durable. 



" As shown in the drawing, the frame should slope 

 toward the su"n and should be six inches higher on the 

 back than on the front side. The top of the frame 

 should be level from east to west." 



Hotbed, — pipe-Jieated. 



A type of hotbed rapidly gaining in favor among the 

 commercial plant-growers of the northern areas is one 

 heated by means of hot water or steam pipe lines, which 

 may be supplied from a greenhouse boiler or a separate 

 heating furnace. The lines of pipe are commonly laid 

 4 or 5 inches below the bed surface. Miller ^ describes 

 the method as follows : " Where a steam or hot-water 

 boiler is used for heating a greenhouse, residence or 

 other structure, it can often be employed to good ad- 

 vantage in heating the sweet potato bed. In fact, where 

 sweet potato plants are grown on a very large scale it 

 might be advisable to install hot water or steam heat 

 even if it is not used for other purposes. The tem- 

 perature of the bed can be regulated more easily where 

 1 Farmers' Bull. 999, U. S. Dept. Agr., page 11. 



