Plants as Affected by Fungous Parasites. 185 



other diseases, but it is less enduring in its effects than 

 the copper compounds. To prepare it, dissolve one- 

 half ounce of potassium sulfid (sulfuret of potassium, 

 liver of sulfur) in one gallon of water and apply im- 

 mediately. The sulfid is best dissolved in a little warm 

 water and then diluted. 



333. Moisture Favors Spore Germination, hence a 

 free circulation of air through the orchard and vine- 

 yard tends to prevent fungous diseases by absorbing 

 excessive moisture (226). Branches of fruit trees should 

 not be permitted to hang near 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 train- 

 ing 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 



* Uncinula spiralis. f Podosphcera oxycanthce. 

 13 



