BY curnirGS of immatuee gkowths. 159 



The slope of the roof should be at an angle of from thii-ty- 

 five to forty-five degrees, varying somewhat according to 

 latitude, although water, snow and ice wiU pass off more 

 readily from a steep roof than a flat one. A single roof, 

 or lean-to, propagating house is perhaps a little more 

 economical than a span roof in very cold climates ; being 

 less exposed to cold winds, it takes less fuel to heat it. 

 Its construction and interior arrangement may be the 

 same as the span roof, only the center frame, or table, is 

 divided lengthways by the main or back wall, which 

 should run east and west, in order to have the roof slope 

 to the south. The lean-to house may be just one half 

 the width of the span roof, or a little wider if necessary, 

 and the furnace-room, potting and storing sheds, should 

 extend the entire length of the back wall as a protection. 

 While professional gardeners depend mainly on a regu- 

 larly constructed propagating house for multiplying those 



Fif;. 54.— LATH SOKEENS. 



plants requiring artificial heat to force them to produce 

 roots, they often employ other means and structures, 

 such as the ordinary hot-bed, where a high temperature 

 and bottom heat are secured by the use of stable manure, 

 leaves from the woods, spent hops, and other kinds of 

 fresh vegetable substances, which generate heat during 

 fermentation. In summer the ordinary hot-bed frames 

 may be employed without bottom heat for multiplying 

 many kinds of plants from green cuttings, especially 

 those known to produce roots freely and with little care. 



