PROPAGATION BY SIKGLE BUBS. 29 



this purpose various materials arc used, such as tan bark, 

 leaves, hops that have been used by the brewers, etc. ; 

 in fact, almost any fibrous material may be used, that 

 will continue to ferment a sufficient time to produce the 

 amount of heat necessary to cause seeds and cuttings to 

 grow, and keep the soil and atmosphere within the bed 

 from twenty to forty degrees above the freezing point, 

 even if the atmosphere without is far below. Besides 

 the materials for producing this heat, we must have a 

 structure called hotbed frames, in which we may control 

 it when generated. These are made of planks of any 

 required size, with a sloping top covered with sash. 

 They may be of any length or breadth, but they are 

 usually four to six feet wide, and of any convenient 

 length. 



The sashes are made without cross-bars, and of a 

 length sufficient to cover the frames crosswise. If the 

 frames are six feet wide, then the sashes may be six feet 

 long and four feet wide ; but if the frames are but four 

 feet wide, the sash may be three by four ; these are con- 

 venient sizes. The size of the glass is immaterial, but 

 six-by-eight and eight-by-ten are sizes commonly used. 

 As there are no cross-bars to the sash, each pane of 

 glass is made to overlap the one below it from one-fourth 

 to one-half an inch, like the shingles on a house. The 

 more the glass overlaps, the more liable it is to be broken 

 by the freezing of the water, which will always accumu- 

 late, more or less, between the panes. The glass should 

 be bedded in soft putty, and fastened with glaziers' 

 points, the sash well painted ; but put no putty upon 

 the upper side of the glass. If anything is needed to 

 stop the joints between the edges of the glass and sash, 

 apply thick paint. If the glass is well bedded in putty, 

 nothing more than painting the upper side will be 

 required, and they are far better without the putty than 

 with it. 



