204 



Principles of Plant Culture. 



Although affording no bottom heat (362 a), the cold- 

 frame may be used for propagating many plants from 

 cuttings. It is also serviceable in connection with the 

 propagating bed (368) for "hardening off" young 

 plants grown from cuttings in the latter, as well as for 

 growing many plants from seed. Set over a pit in the 

 earth, the cold-frame makes an excellent place (cold 

 pit) for wintering half-hardy plants. 



365. The Hotbed differs from the cold-frame in hav- 

 ing bottom heat (362 a), which is usually supplied by 

 the fermentation of moist vegetable material, as horse 

 manure, leaves, refuse hops or tan bark. The material 

 intended for heating, if fresh, should be thrown into 

 a pile of sufficient size to generate heat several days 

 before it is desired for use ; and unless already moist, 

 it should be moderately sprinkled with water. In or- 

 der that all the material may reach the same stage of 

 fermentation, the mass should be made into a new pile 

 after the heating starts vigorously, as is indicated by 



vapor rising 

 from the heap, 

 and the outer 

 part of the mass 

 should be placed 

 in the center of 

 the new pile, 



FIG. 94. Cross -section of hotbed in pit. The Leaves ferment 

 frame is banked up a little with earth. (After 



Qreiner.) slower than the 



other materials above named, and hence may often be 

 advantageously mixed with them to lengthen the period 

 of fermentation. 



