DISEASES OP PLANTS. 249 



Iho aniniinl rcinainins ■■iiul tlu> orisinal anionnt is givon as the coefficient of 

 adhesion. 



The fiiniLj;ici(los tested were Bordeaux mixture, soda Bordeaux, copper acetate 

 sohitions, annnoniacal copper carbonate solution, and several special trade prepa- 

 rations. Ail the fungicides were so prepared as to contain approximately the 

 same amounts of copjier. 



In the sununary of the author's' conclusions it is shown that the alkaline Bor- 

 deaux mixture made hy what is termed the American method and the same 

 mixture to which molasses or linseed oil was added were the most adhesive, 

 from 90 to 95 per cent of the copper remaining on the leaves. Neutral Bor- 

 deaux mixture had a coefficient of 75 to 80 per cent, and acid Bordeaux mixture 

 50 to 55 per cent. The adhesiveness is said to be diminished by mixing the 

 copper sulphate and lime in too concentrated forms. Delaj^ in application after 

 preparation reduces adhesiveness, although the molasses Bordeaux mixture re- 

 tains its coefficient of adhesiveness after standing for 48 hours. Neutral soda Bor- 

 deaux mixture had a coefficient of 85 per cent when made by the American 

 method. Where this mixture was alkaline 72 to 75 per cent remained on the 

 leaves. When freshly prepared from dry powdered chemicals it had a coefficient 

 of 70 to 75 per cent, but if the powders were allowed to stand for several hours 

 the adhesiveness fell to 50 per cent or less. This was also found true for a 

 number of proprietary mixtures which are sold in powdered form. All the mix- 

 tures containing carbonate of soda lost their adhesiveness rapidly, and after 

 standing during 2 days of warm weather prior to application to the foliage all 

 traces of copper were removed by the washing process. Mixtures to which 

 soap or sugar was added differed but little from ordinary soda Bordeaux mix- 

 ture in their adherence. 



In general the copper acetate solutions were less adherent than those described 

 above. Neutral copper acetate had a coefficient of 50 to 52 per cent, but by the 

 addition of sulphate of soda it was increased to 58 to 65 per cent. By the addi- 

 tion of kaolin to neutral copper acetate the coefficient of adhesiveness was 

 increased to 65 to 72 per cent, and where ammonia was added it was increased 

 to 80 to 83 per cent. The copper acetate and ammoniacal solutions did not seem 

 to depreciate very much on standing. Eau celeste had a coefficient of 56 to 58 

 per cent, ammoniacal copper carbonate solution 73 to 76 per cent, and copper 

 formate 82 to 83 per cent. 



In practice the forms of Bordeaux mixture give the best results, but they 

 offer many difficulties of preparation and application that the copper acetate 

 solutions do not. On this account the author believes that solutions will prob- 

 ably be found adapted to general use, although their adherence to the foliage is 

 not as perfect as those fimgicides containing lime. 



The use of dilute solutions of sulphuric acid as a fungicide. H. Keaemer 

 (Science, n. scr., 28 {1906), Isio. 599, p. 9Jil). — In a paper presented at the cele- 

 bration of the two-hundredth anniversary of the birth of Benjamin Franklin, 

 the author gives the results of the use of dilute solutions of sulphuric acid as 

 a fungicide for preventing the mildew on roses. 



The fungicide was tested on plants growing outdoors as well as in the 

 greenhouse, and the application of a solution containing approximately 1 part 

 of sulphuric acid to 1,000 parts of water was employed. The roses were unin- 

 jured by the acid solution, and they began immediately to develop new leaves 

 and young shoots entirely free from mildew after from 3 to 6 applications on 

 alternate days. Should subsequent experiments confirm these observations, the 

 use of sulphuric acid will have certain advantages over the use of sulphur, as 

 it does not discolor the foliage and its employment is more easily controlled. 



