DISEASES OF GINSENG. 109 



stroyed at the same time, add about four ounces paris green to 

 each fifty gallons of bordeaux.) It is important that the mixing 

 of the two solutions is done as above stated. 



Never mix more than enough for the day's use, for the two 

 solutions, after they are mixed, will deteriorate. Separated, or 

 what we have above termed stock solutions, can be kept all sum- 

 mer unimpaired. 



HOW TO TEST BORDEAUX. Bordeaux may be tested, to deter- 

 mine whether a suiBcient quantity of the lime solution has been add- 

 ed to neutralize the caustic action of the copper sulphate, with 

 ferrocyanide of potassium (yellow prussiate of potash). 



The preparation of ferrocyanide of potassium for this test 

 is simple. As bought at the drug store, it is a yellow crystal and 

 is easily soluble in water. Ten cents worth will do for a seasons 

 spraying of a large garden. It should be a full saturation; that 

 is, use only enough water to dissolve all the crystals. The cork 

 of the bottle should be notched, or a quill inserted, so that the con- 

 tents will come out in drops. A drop will give as reliable a test as 

 a spoonful. The bottle should be marked ,, Poison." Dip out a 

 little of the Bordeaux mixture in a cup or saucer and drop the 

 ferrocyanide on it. So long as the drops turn brown on striking 

 the mixture, the mixture has not received enough lime. Add more 

 lime water until no change takes place. After that, add a little 

 more lime water to make the necessary amount of lime a sure 

 thing. A considerable excess of lime does no harm, while not 

 enough may cause burning of the plants. It is always well to test 

 Bordeaux mixture by using the ferrocyanide of potassium. 



