Propagation and Care of Plants 67 



A soil suitable for seed boxes ought to have sufficient The right 

 sand and humus to keep it from forming a crust. One- ^Idboxes 

 third ordinary soil, one-third sand, and one-third leaf 

 mold makes a good mixture. 



Packing the soil, as we have seen, is accomplished in Peaking the 

 the field by means of a roller or a subsurface packer. * 

 In the greenhouse a flat wooden block called a " float " 

 is used to firm the earth in the seed boxes. The surface Tools used 

 in both cases is afterwards made loose, in the field 

 by harrowing and in the greenhouse by sifting a layer of 

 fine soil on top of the packed soil in the seed boxes. 

 In the garden a rake is used in making the mulch. 



A rule often given for greenhouse planting is this, Depth of 

 that a seed should be covered with a layer of soil equal 

 to its own thickness. Thus a coconut might be placed 

 about seven inches underground, but such fine seeds 

 as those of the begonia should have as little cover- 

 ing as possible. They are sometimes covered only 

 with a damp cloth, which is removed when the seeds are 

 sprouted. 



A small seed must be near the surface because the new Why small 

 plant cannof*begin to draw nourishment from the air 

 until it comes up into the light. If it has far to come, 

 it may die of starvation before it reaches the surface. 

 A large seed, having a greater store of nourishment, 

 may send up a shoot through several inches of soil be- 

 fore the young plant needs to depend upon food of its 

 own making. 



In the field and garden, where the surface of the ground Rules for 

 is very dry and moisture from below is relied upon to planting 

 cause germination, the seeds must be put deep enough 



