Propagation by Cuttinf/x. 195 



covered with glazed window sash.* The frame is gen- 

 erally placed so that its shallower side faces the south, 

 thus giving its cover a southward slope. It has no 

 provision for artificial heat, though when covered with 

 glass, the temperature within the frame is much increas- 

 ed during sunshine, owing to the property possessed by 

 glass of confining the heat rays. The cold frame should 

 be protected in freezing weather by an additional cover 

 of mats or blankets, while excessive sun heat should be 

 avoided by shading (236). Muslin- or paper-covered 

 frames require no shading. 



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 having 

 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 order that all the 

 material may reach the same stage of fermentation, the 

 mass should be made into a new pile after the heating 



* Muslin or paper is sometimes used instead of glass, and these mate- 

 rials maybe rendered waterproof and less opaque by painting with linseed 

 oil or some similar material. 



