178 Principles of Plant Culture. 



initted to hang n.ear the ground, and weeds should be 

 kept down. 



Grapes are sometimes inclosed in paper bags on the 

 vine, to keep them dry, and thus preserve them from 

 fungous attack. Grape vines sheltered from rains by a 

 cornice are seldom much troubled with fungous diseases. 



334. Fungi that Develop chiefly on the Outside of the 

 Plant (epiphytic (ep-i-phyt'-ic) fungi), are as a rule readily 

 controlled by sulfur, either in the form of flowers of sulfur, 

 or the solution of potassium sulfid (332). To this class 

 belong the powdery mildews of the grape,* apple, f etc. 



335. The Cultivator will often Need to Consult the 

 Specialist in dealing with fungous diseases. In many 

 cases, it will be difficult or impossible for him to decide 

 as to the exact nature of a given trouble without careful 

 training, and skill in the use of the compound microscope. 

 Specialists in this line are now employed by the govern- 

 ments of most civilized nations and by many agricul- 

 tural experiment stations, and they should be freely con- 

 sulted. Much may be learned, however, by studying 

 the best books on the subject. The cultivator should be 



able to recognize the principal fungous diseases. 



i 



SECTION VIII. PLANTS AS AFFECTED BY WEEDS 



336. Weeds are plants of the higher orders that persist 

 in growing where they are not wanted. They injure the 

 desirable plants about which they grow, by robbing them 

 of light, moisture and food, and their presence is an evi- 

 dence of slovenly culture. The remarkable vigor and 

 prolificacy possessed by many weeds would enable them 



* Uncinula spiralis. f Podosphcera oxycanthce. 



