180 Principles of Plant Culture. 



stems whence the suckers grow (115), are hidden be- 

 neath the soil and are often extremely tenacious of life, 

 weeds of this class are frequently very hard to eradicate. 

 Persistent prevention of leafage, by starving the proto- 

 plasm of the roots, is always effectual, though it is often 

 very difficult to carry out, since the suckers of some 

 species grow with great rapidity. Yet, on the whole, no 

 better remedy is known. Frequent plowing and cultiva- 

 tion of the infested ground is usually the most effectual 

 means of preventing leafage. 



Certain very tenacious perennial weeds, as the Canada 

 thistle * and the sow thistle, f when growing on deep, rich 

 loams in which the roots spread freely below the plow 

 line, may, it is said, be crowded out by seeding the land to 

 grass, at less cost than they can be subdued by the plow. 



If we have mastered the foregoing chapters, we are 

 now 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 

 connection with the preceding chapter: Elementary 

 Meteorology, Waldo; Chemistry of the Farm, Waring- 

 ton; The Spraying of Plants, Lodernan; Economic En- 

 tomology, Smith; Fungous Diseases of the Grape and 

 Other Plants, Lamson-Scribner; American Weeds and 

 Useful Plants, Darlington. 



* Cnicus arvensis. t Sonchus arvensis. 



