68 The Principles of Vegetable -Gardening 



made directly in the field where the plants are to 

 remain, and the frames, and not the plants, are re- 

 moved. When used for this latter purpose, the frames 

 are made very cheap by running two rows of parallel 

 planks through the field at a distance of six feet 

 apart. The plank on the north is ordinarily 10 to 

 12 inches wide, and that on the south 8 to 10 inches. 

 These planks are held in place by stakes, and the 



Fig. 19. A span-roof coldframe, or cold forcing-house. 



sash are laid across them. Seeds of radishes, beets, 

 lettuce, and the like, are then sown beneath the sash, 

 and when settled weather arrives the sash and planks 

 are removed and the plants are growing naturally in 

 the field. Half-hardy plants, like those mentioned, 

 may be started two or three weeks in advance of the 

 normal season by this means. 



When the heat is spent from hotbeds, they become 

 coldframes. They can then be used, if empty, for the 

 starting of late plants ; or the plants may be hardened- 



