178 



a portion of whose mycelium lives over winter within 

 the host plant itself. In fact in the case of the particu- 

 lar fungus causing this disease no part of the mycelium 

 enters the host plant farther than directly beneath the 

 cuticle of the leaf. 



During the spring of 1902 an attempt was made to pre- 

 vent the appearance of the disease upon a specimen of 

 the water oak, Qncrcus nigra. The ordinary Bordeaux 

 mixture was employed, made according to the following 

 formula : 



Copper sulfat or "blue vitrol' ' .... 4 lbs. 



Unslaked lime 4 lbs. 



Water 50 gallons. 



Place the copper in a coarse cloth sack and dissolve 

 it by suspending the sack in a wooden vessel holding 

 abont 15 gallons of water. The lime is then to be slaked 

 with just enough water to ensure thorough slaking. The 

 slaked lime is then to be made into a paste having the 

 consistencv of thick cream bv adding water and stirring. 

 When the solutions thus prepared are cold the lime 

 water is to be poured into the copper sulfat solutioil 

 through a fine sieve. Water is then to be added to make 

 the solution up to the required 50 gallons and the whole 

 thoroughly stirred before and while using. If too little 

 lime has been employed the solution may injure tender 

 foliage and the potassium ferr^Tonaid test should be ap- 

 plied to determine this point. The test consists in add- 

 ing to a small sample of the prepared mixture a few 

 drops of a solution of potassium feiTocyanid made by 

 adding one part by weight of the salt to five parts of wat- 

 er. If, upon the addition of a few drops of this solution, 

 the bordeaux mixture becomes a reddish-brown one may 

 knoA^' that not enough lime has been employed in the prep- 

 aration of the spraying solution. After the addition of 

 more lime test again in the same manner and consider 



