90 PHYSIOLOGICAL RELATIONS 



constant stirring. The mixture is then brought up to 50 gallons. 

 Ammoniacal copper carbonate should be used as promptly as 

 possible, owing to the rapid evaporation of the ammonia. 



Lime-sulfur wash. The lime-sulfur preparation which may be 

 employed with least fear of injury to growing plants is a form 

 known as " self -cooked." It has been introduced relatively re- 

 cently, and, therefore, has not been extensively employed by com- 

 mercial growers. The constituents are as follows : 



Flowers of sulfur 10 Ib. 



Stone lime 10 Ib. 



Water 50 gal. 



The preparation of the mixture is simple. After weighing the 

 lime into a barrel add three gallons of water, sift in the sulfur, 

 and slake the lime slowly. As heating proceeds add more water 

 and stir occasionally. The heat developed is sufficient to " cook " 

 to the extent desired. When completely slaked cool promptly by 

 diluting to fifty gallons. Patent preparations are made. 



Potassium sulfide. Potassium sulfide is a fungicide which is 

 also employed when it is undesirable to have foliage discolored. 

 It is, moreover, believed to be especially effective in the preven- 

 tion of certain mildews, especially that of the gooseberry, and 

 also the rust of carnations. This substance is sometimes known 

 as liver of sulfur, and should, when fresh, make a solution 

 yellowish brown. It is employed in the following preparation : 



Potassium sulfide 3-5 oz. 



Water 10 gal. 



Sulfur. Flowers of sulfur is often surprisingly effective in the 

 treatment of certain surface mildews, such as that of the rose. 

 It may be dusted over the plants so as to fairly cover them with 

 the yellow powder, and is particularly effective when the plants 

 are wet. A paste of sulfur and lime is also employed by many 

 growers in rose houses, the method of application being then to 

 smear the steam pipes with the mixture, the fumes from which 

 are disastrous to the mildew. 



Recently a sulfuric acid solution of a strength of i-iooo has 

 also been successfully employed in the treatment of rose mildew 

 and similar fungi. 



