Germination of Forest Trees 85 
This diagram shows very strikingly the water retaining capacity 
of these three soils. Not only do sand and gravel hold less mois- 
ture at the time of watering but they lose a much greater per 
cent. of it in the course of twenty-four hours than does loam. 
Sand grave/ 
Diagram showing: 
L]soil moisture per cent. at time of watering; 
fj soil moisture per cent. twenty-four hours later. 
When we consider the amount of air space in these soils and the 
amount of soil moisture each retains, the fact that loam usually 
contains a great deal of moisture and very little air space and that 
gravel contains very little moisture and a great volume of air 
Space is very strikingly shown. 
