174 Principles of Plant Culture. 
loams in which the horizontal roots extend freely below the 
plow line, may, it is said, be crowded out by seeding the 
land to grass, at a less cost than they can be subdued by 
the plow. 
Having now carefully studied the round of plant life, and 
how plants are affected by unfavorable conditions of envi- 
ronment, we are prepared to enter upon a more advanced 
stage of culture, and to learn how to cause new plants to 
grow, and how to so treat the plants thus grown that they 
may best serve our purpose. 
The following books are recommended for reading in con- 
nection with the preceding chapter: Elementary Meteorol- 
ogy, Davis; Chemistry of the Farm, Warington; Agricul- 
ture, Storer; The Spraying of Plants, Lodeman; Economic 
Entomology, Smith; Manual for the Study of Insects, Com- 
stock; Fungous Diseases of the Grape and Other Plants, 
Lamson-Scribner. 
