186 Principles of Plant Culture. 



consulted. Much may be learned, however, by studying 

 the best books on the subject. The cultivator should 

 be able to recognize the principal fungous diseases. 



SECTION VIII. PLANTS AS AFFECTED BY WEEDS 



336. Weeds are plants of the higher orders that per- 

 sist in growing where they are not wanted. They in- 

 jure the desirable plants about which they grow by 

 robbing them of light, moisture and food, and their 

 presence is an evidence of slovenly culture. The re- 

 markable vigor and prolificacy possessed by many weeds 

 would enable them to soon overcome most cultivated 

 plants, but for the aid of the cultivator. As with 

 harmful insects and fungi, prompt and persistent ef- 

 forts are essential to the control of weeds in most cul- 

 tivated grounds. 



337. Annual, Biennial and Perennial Weeds. With 

 reference to their term of life, weeds and other plants 

 are divisible into three classes, viz., annual, those that 

 live but one season; biennial, those that live only two 

 seasons; and perennial, those that live an indefinite 

 number of seasons. Weeds of the first class usually 

 seed most abundantly, and hence they are most widely 

 distributed and appear in cultivated grounds in the 

 greatest numbers. Those of the third class are com- 

 monly most tenacious of life and are therefore often 

 most difficult to control. 



338. Annual and biennial weeds, since they have a 

 definite life period and multiply almost exclusively by 

 seed, may be controlled by preventing seedage. To ac- 

 complish this with certainty, the plants should be de- 



