82 Richard H. Boerker 
the difference in both cases is greater for the variety that comes 
from the drier climate, that is, the South Dakota variety of Pinus 
ponderosa shows a greater difference than the Idaho variety and 
the New Mexico variety of Pseudotsuga taxifolia shows a greater 
difference than the Colorado. ‘The data here presented upon this 
phase of the problem, however, are not sufficient to warrant 
conclusions. 
GENERAL SUMMARY AND CONCLUSIONS 
I. The Effect of Habitat Factors upon Germination 
1. Shade decreases evaporation and transpiration and thereby 
increases the Soil-moisture content of the superficial soil layers. 
This increase in soil moisture content is best shown by the ac- 
companying diagram. ‘This conclusion agrees with the results 
obtained by Stewart and Hasselbring who grew tobacco in shade 
tents. 
2. Shade accelerates germination, that is seeds germinate 
sooner in the shade than in the light. This acceleration is due 
to the increase in sotl-moisture content spoken about above. 
Oo 
opey medium deyse 
light Shade shade 
Diagram showing soil moisture content in the three light cultures. 
