THE PROPAGATION OF PLANTS 



203 



bench is boxed in with boards. Horizontal doors are, 

 however, provided, which may be opened when it is desir- 

 able to allow a part of the heat to pass directly into the 

 house. The floor of the bench should not be so tight as 

 to hinder drainage. 



In large commercial establishments, entire glass houses 

 are often devoted solely to propagation. Sometimes 

 lean-to houses are built for propagation, on the north 

 side of a wall, where direct sunlight 

 is cut off. 



In making the propagating-bed, a 

 thin layer of sphag- 

 num moss is usually 

 spread over the floor 

 of the bench and cov- 

 ered to a depth of two 

 to four inches with 

 well-packed, clean, 

 rather coarse sharp 

 sand, or other material 

 which will not retain 

 an excess of water if 

 the proper provision 

 is made for drainage. 

 Sometimes the whole bed is made of moss. Sand is 

 most used because it is as a rule readily obtained, but 

 it needs to be selected with care, as it often contains 

 injurious mineral matters. Sand found along the bor- 

 ders of fresh-water streams or lakes may generally be 

 used without washing, but that dug from sand pits 

 should in most cases be exposed to the air for a few 

 weeks, and then be thoroughly washed before being 

 employed for cuttings. It should be relatively free from 



FIG. 99. Propagating-bed covered with 

 glazed sash. 



