86 A7i7ials of Horticulture. 



always will be the available form in which copper will be most 

 effective against mildew, and this solution alone fulfils all the 

 necessary conditions, viz : 



''I. Absolute certainty of never burning, whatever the 

 amount applied. 



''2. Ease of preparation. 



''3. Solution obtained without the addition of any other 

 substance. 



"4. Copper dissolves without the addition of any other 

 substance. 



''5. The ease with which the substance remains in sus- 

 pension. 



''6. Immediate destructive action against mildew. 



" 7. Complete adherence to the leaves. 



''8. Indefinite preservation. 



''9. Natural richness in the hydrate of the binoxide of 

 copper. 



" 10. Cheapness. 



''II. Required number of applications as small as possible. 



"One of the failings of the Bordeaux mixture, and of the 

 carbonate of soda and sulphate of copper, is that they do not 

 contain sufficient dissolved copper. This defecft might be re- 

 medied in the laboratory but it is impracticable to do so in the 

 field. Sugar and lime have been the principal agents used 

 for this purpose, giving rise to two classes of fungicides — 

 those prepared in the laboratory, and those made by the grow- 

 er. The preparation of either kind is difficult and expensive. 

 The same results do not always follow the use of the same 

 proportions of the ingredients. Sometimes more and some- 

 times less lime is required to exactly precipitate all the sul- 

 phate ; and again a certain amount of sugar does not always 

 dissolve a corresponding amount of the oxide. Nor does the 

 preparation retain a uniform strength. Its action grows 

 weaker so that only the amount to be used immediately should 

 be prepared. A still more serious objection is, that the 

 amount of lime or soda used to neutralize the acid may not 

 be sufficient, and consequently the valuable sulphates remain- 

 ing would, when applied, seriously burn the foliage. 



" In the improved Bordeax mixture the most difficult opera- 

 tions have already been made. One admirable quality is the 

 ease with which it remains in suspension. Its cost is about 

 45 cents per hectolitre. In regard to adhesion and durability 



