SECTION OF VEGETABLE PATHOLOGY. 331 
phate of copper in the solution by the addition of more water, the 
simple solutions had best be discarded in treatments during the grow- 
ing season. : 
Kau celeste also has, in the haiids of some, injured the foliage ma- 
terially, and a modification of the original formula is suggested in 
order to overcome this danger. In 2 gallons of hot water dissolve 1 
pound sulphate of copper, in another vessel dissolve 2 pounds of ordi- 
nary carbonate of soda; mix the two solutions, and when all reaction 
has ceased add 14 pints of liquid ammonia; when desired for use, 
dilute to 22 gallons.* 
It is stated+ that all danger of injury to the foliage from the first 
applications, made while the shoots are yet young and tender, may 
be entirely overcome by preparing the eau celeste for the first treat- 
meant in the following manner: Dissolve 1 pound sulphate of copper 
in a gallon of hot water, to this solution add liquid ammonia, a little 
at a time, until all the copper is precipitated ; the liquid is then tur- 
bid and blue in color. Add two or three gallons of water and let 
‘stand to settle. Then pour off the clear liquid which contains sul- 
hate of ammonia—the compound which causes the burning of the 
eaves. Then pour uponthe precipitate left in the vessel Just enough 
liquid ammonia to dissolve it. The result is a clear liquid of a beau- 
tiful deep blue color. When required for use dilute to 22 gallons. 
Eau celeste prepared in the ordinary manner may be used without 
fear after the vines are in full foliage. 
oS 
Considerable latitude is allowed in quantity of lime and copper sul- 
phate in the Bordeaux mixture, but the amount of the latter ought 
not to fall below 4 per cent. The most recently recommended form- 
ula for preparation of this compound is 4 pounds of sulphate of copper, 
2 pounds lime, 25 gallons water.{ This reduces very much the cost 
of material, and the labor in applying is far less than when pre- 
pared according to the original formula, but some have found it to 
be inefficient. 
Ii1.—PorTaTo BLIGHT AND ROT. 
The value of eau celeste and the Bordeaux mixture in treating po- 
tato blight and rot (caused by Phytophthora infestans) has been fre- 
quently stated in France, and the very great need of discovering 
effective means for checking these diseases in this country was the 
occasion for preparing the following circular, which the Commis- 
sioner ordered to be printed and distributed : 
(Section of Vegetable Pathology.—Circular No. 4.] 
Treatment of the potato and tomato for the blight and rot. 
_ Sir: In Circular No. 3 of this section, addressed to the vineyardists of the country, 
it was suggested that some of the preparations therein described might be found use- 
fulin preventing potato ‘‘ blight” and “rot,” this suggestion being made upon the 
knowledge of the fact that the fungus which causes the mildew of the vine is very 
similar in character to that which produces the diseases named above. The pub- 
lished evidence of experiments made in France, in 1886, in the treatment of pota- 
toes and tomatoes for “‘ blight” and ‘‘ rot” with the Bordeaux mixture, gives addi- 
tional weight to this subject and renders it highly probable that by the application 
* Formula of M. Masson, Progrés Agricole, July, 1887, 
+ ‘“Progrés Agricole et Viticole,” April 29, 1888. 
} Viala and Ferrouillat, ‘‘ Manuel pratique pour le Traitement des Maladies de la 
Vigne,” 2d ed., Mar., 1888, p. 27. 
