$2 



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 



i. 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 soil-moisture content spoken about above. 



zo 



/o 



f'ght shade. ' shade 



Diagram showing soil moisture content in the three light cultures. 



