86 Richard H. Boerker 
Il. The Effect of Habitat Factors upon Stem and Root 
Development 
1. Pinus ponderosa and Pinus strobus show increased height 
growth with dimimshing 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 Quercus 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 dimimshing light intensity. These 
results again bear out the conclusions of Nikolsky and Burns. 
4. Robinia pseudacacia and Quercus 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 
Quercus rubra show increased height growth with an increase in 
soil depth. : 
6. Pinus ponderosa, Robima pseudacacia, Pinus strobus, and 
Quercus rubra show an increase in length of tap root but a 
decreased development of lateral roots with increased depth of 
soil. 
7. Pus ponderosa, Robinia pseudacacia, and Pinus strobus 
show a decrease in height growth with a decrease in the soil 
moisture supply. 
8. Pius 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. 
it. Robinia pseudacacia and Quercus rubra show the greatest 
