48 The Spraying of Plants. 



In 1891 Millardet and Gayon also made a comparative test 

 of various fungicides. 1 Their work, however, did not consider 

 mainly the adhesive power of the fungicides, but rather their 

 general efficiency. During 1890 they applied the sulphosaccha- 

 rate of copper of B. Pons (see page 42). The downy mildew was 

 not sufficiently severe to show the value of the fungicide and 

 no report could be made. In 1891 Pons sent another prepara- 

 tion to Millardet and Gayon, this being known under the con- 

 venient term " bouillie bordelaise celeste a poudre unique" It 

 was in the form of a very fine blue powder, and was composed 

 essentially of the powder of Bordeaux mixture celeste, sulphate 

 of copper, the carbonate and the bicarbonate of soda. 



The amount of the powder used per hectoliter of water was 

 two kilos, this containing exactly one kilo of copper sulphate. 

 The powder was added to the water, was thoroughly stirred, 

 and then applied. The material is so fine that it settles very 

 slowly, probably not before twenty-four hours ; the liquid 

 above it is blue and contains a little more than one-tenth of 

 the total amount of copper in solution in the form of the bi- 

 carbonate. 



The above preparation was used in comparison with the 

 following : the Bordeaux mixture as commonly made (see page 

 40), Bordeaux mixture celeste (see page 42), Bourguignonne 

 mixture (see page 32), Berrichone mixture of Dr. Patrigeon (see 

 page 37), Bordeaux mixture and the sulphate of ammonia, and 

 Bordeaux mixture and glue (see page 28). The results of these 

 applications were as follows : 



" 1. All the mixtures, containing equal amounts of copper, 

 have shown an equal degree of efficiency, and the attack of 

 mildew was severe. The mixture containing the sulphate of 

 ammonia burned the foliage occasionally and is therefore more 

 uncertain in its action than are the others. 



" 2. The mixtures which contain copper in a state of solution 

 do not appear to be more active than the common Bordeaux 

 mixture and the Bourguignonne mixture, each of which con- 

 tains none. In no case was there for some time a hard rain 

 after the applications, a circumstance which should diminish 

 the .efficiency of these two preparations, and augment compar- 

 atively the efficiency of the others. 



1 Jour. tfAg. Prat. 1892, Feb. 18, 231. 



