86 Richard H. Boerker 



II. The Effect of Habitat Factors upon Stem and Root 



Development 



i. Pinus ponder osa and Pinus strobus show increased height 

 growth with diminishing light intensity. This conclusion bears 

 out the results secured by Nikolsky who worked with pine and 

 spruce and Burns who worked with Pinus strobus. On the other 

 hand Badoux showed that pines decrease their height growth 

 with increasing shade; but these trees were grown to a height of 

 about six feet while Nikolsky and Burns experimented with much 

 smaller stock. 



2. Robinia pseudacacia and Oucrcus rubra show a decrease in 

 height growth with diminishing light intensity. 



3. Pinus ponderosa shows a decrease in length of tap root and 

 in total length of laterals with diminishing light intensity. These 

 results again bear out the conclusions of Nikolsky and Burns. 



4. Robinia pseudacacia and Oucrcus rubra show a decrease in 

 length of tap root and total length of lateral roots with decreased 

 light intensity. 



5. Pinus ponderosa, Robinia pseudacacia, Pinus strobus, and 

 Oucrcus rubra show increased height growth with an increase in 

 soil depth. 



6. Pinus ponderosa, Robinia pseudacacia, Pinus strobus, and 

 Oucrcus rubra show an increase in length of tap root but a 

 decreased development of lateral roots with increased depth of 

 soil. 



7. Piuus ponderosa, Robinia pseudacacia, and Pinus strobus 

 show a decrease in height growth with a decrease in the soil 

 moisture supply. 



8. Pinus ponderosa shows an increase in length of tap root 

 and an increase in total length of lateral roots with diminishing 

 soil moisture content. 



9. Robinia shows a decrease in length of tap root with a de- 

 crease in soil moisture supply. 



10. Pinus ponderosa shows the greatest height growth in the 

 loam and gravel, but Pinus strobus shows the greatest height 

 growth in the sand. 



11. Robinia pseudacacia and Oucrcus rubra show the greatest 



