RESEARCH METHODS IN STUDY OF FOREST ENVIRONMENT. 
89 
2. The group averages for the loamy spruce soils and the granitic 
gravels are essentially the same. It therefore seems entirely legiti- 
mate to consider both groups together and, as shown in diagram 4, 
to express the relation of wilting coefficient to capillarity by a straight 
line. The nineteen cases show an average variation of 0.0333 from 
the mean ratio of 0.202, or 16.5 per cent variation. 
3. Both from its mean value and from the fact that the graph 
which expresses this relationship passes through the main axis of 
the system of coordinates it is evident that the capillary moisture as 
it has been measured by the method described above is an entirely 
MEAN 
?o 
DIAGRAM 4 
RELATION Or 
WILTING COEFFICIENT TO CAPILLARY MOISTURE 
IN 10 SPRUCE SOILS AND 9 GRAVELS 
LEGEND 
2.75 Humus percen+ate 
O SPRUCE GRANITIC LOAMS 
650 Solutes, p-pm. of soil wl 
a GRANITIC GRAVELS 

us; 
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045 
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it 
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different expression from that used by Hilgard and by Briggs and 
Shantz. 
4. The relatively high wilting coefficients of the loamy soils having 
the largest humus contents are believed to result from experimental 
errors, largely unavoidable, and due to the lack of capillary con- 
ductivity in soils which are particularly loose. This lack permits a 
seedling to succumb in one region of the soil, while there may be 
considerable free moisture elsewhere. The two srravellv soils which 
show similarly high wilting coefficients also have high moisture 
equivalents, and it is thought from this that they were probably 
richer than usual in permeable feldspar, which could not hold much 
water but would probably hold it very firmly. 
