Pla7it Diseases and Insects. 85 



''Powders. Although it is advisable to use liquids when 

 possible, those who find this method of treatment impracti- 

 cable will obtain good results with powders, especially cupro- 

 steatite. In the powder cupro-phosphate, the sulphate of copper 

 is in the form of a hydrate, and thus cannot burn. The phos- 

 phate of lime, in which this oxide is found, is also a fertilizer 

 for grapes ; certainly this is an advantage, but is it not to the 

 detriment of the adhesive quality? We must not lose sight 

 of the fact that we are trying to destroy the mildew ; the mixed 

 powders (sulphate and the salts of copper), designed to guard 

 against the oidium and the mildew, are not very successful. 

 It is better to combat the diseases separately, although at the 

 national school last year the sulphur of Skawinski was found 

 more effective against mildew than Skawinski's powder. 

 Plainly here was an anomaly. 



"Liquids. This year Mr. Duchein wished to try a fungi- 

 cide having aluminium for its essential ingredient instead of 

 copper. It is composed of 2 k. of alum to i k. of chloride 

 calcium, used in the proportion of 5^ k. to a hectolitre of 

 water. Since the mildew did not appear, the value of this 

 compound could not be determined, but there is little reason 

 to believe that it would prove more valuable than the bouillie 

 biteri'oise which contains no copper and which was not used at 

 all this year, as it has been found to be worthless. 



"The gelatinous hydro-carbonate of copper would have been 

 better than the preceding, but in regard to adherence and 

 durability it is far from being equal to the carbonate of soda 

 and sulphate of copper. 



"Sporivore is a glue which is added in the proportion of i 

 k. in a hectolitre of water to a Bordeaux mixture consisting of 

 I k. of sulphate of copper and i k. of lime. This material is 

 still less adhesive than the hydrocarbonate ; besides, when 

 applied, it covered the leaves with an impermeable coating, so 

 that they drooped from want of air. But fortunately this was 

 washed off and growth recommenced. 



"This proves the error of those who wish to make the Bor- 

 deaux mixture more adhesive by adding some substance such 

 as gelatine, gum, glue, etc. Adhesion should be obtained only 

 by means of soluble salts which recrystallize on the leaves in 

 the form of a tightly fitting net. 



" In 1887 we maintained that a solution of verdet is and 



