Propagation by Cuttings. 203 



plants, as the willow, grape and currant, are readily 

 propagated from cuttings out of doors. Some struc- 

 ture, therefore, that may confine warmth radiated from 

 the earth or artificially generated, or that may when 

 necessary shut out a part of the solar heat, is always of 



great assistance 

 i n propagating 

 plants from cut- 

 tings, and in 

 many species is 

 essential to suc- 



FIG. 93. Cold-frame, with sash lifted for o . v , , 



ventilation. C6SS. Since light 



is necessary to food preparation (58), such a structure 

 must be roofed with glass or some other more or less 

 transparent material. 



364. The Cold-Frame (Fig. 93) is the simplest struc- 

 ture of this kind. It consists of a frame or box with- 

 out bottom, usually shallower on one side than on the 

 other, covered with glazed window sash.* The frame 

 is generally 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 

 increased during sunshine, owing to the property pos- 

 sessed by glass for 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 (235). Muslin- 

 or paper-covered frames require no shading. 



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

 materials may be rendered waterproof and less opaque by paint- 

 ing with linseed oil or some similar material. 



