DISEASES OF PLANTS. 51 



Aftor a jreneral review of fnusicides and their aelioii the author classifies the 

 various copper preparations according to the action carbon dioxid exerts upon 

 them. A hirge portion of the work is taken up with studies on the chemistry 

 of Bordeaux mixtures of various kinds, some of the results of which liave been 

 noted elsewhere (E. S. R., 19, p. 450; 20, p. 163; 22, p. 455). A review is given 

 of various reports on the fungicidal action of Bordeaux mixture, after which 

 accounts are presented of the authors' experiments on the scorching effect and 

 fungicidal action of various compounds. 



The etiiciency of fungicides is said to depend on their gradual solution, and 

 the principal solvent agent is the carbon dioxid of the air. The best results are 

 to be obtained with substances which are insoluble at the beginning, but from 

 which small quantities of soluble copper are gradually liberated. The authors 

 state that in making Bordeaux mixture to be economical of material, as little 

 lime should be used as possible, consistent with precipitating all the copper. 

 The lowest basic sulphate which it is possible to make in this way constitutes 

 what has been called the Woburn Bordeaux mixture. This, according to its 

 cliemical composition, should be 2* times as efficient as ordinary Bordeaux 

 mixture. 



An investigation was made of a form of paste which is practically identical 

 with Bordeaux mixture. So far as present investigation is concerned, this 

 seems to be satisfactory and equal to the ordinary freshly prepared Bordeaux 

 mixture. Field trials on an extensiA^e scale, however, are necessary before it 

 can be untiualifiedly recommended. 



Many points in connection with the manufacture and application of Bordeaux 

 mixture were examined, and the conclusion is reached that the best way of 

 making the mixture so as to get the precipitate in its most bulky condition is 

 to have the lime solution as weak as ix)ssible and the copper sulphate solution 

 as strong as possible. This is secured by slaking the lime, making it into milk 

 of lime, and diluting with the amount of water required for the total amount of 

 fungicide. This is allowed to settle for a few minutes and then added to the 

 copper sulphate solution, which should be made in as small a bulk of water as 

 possible. 



In examining the relative efficiency of the different copper compounds it was 

 found that the scorching action of the different salts on tlie leaves was independ- 

 ent of the nature of the copper salt taken and depended solely on the quantity 

 of copper present, A scorching and fungicidal action of solutions containing 

 1 part of copper in 100,000 or 200,000 was observed and it was found to increase 

 \ery slowly with the concentration. Copper in the electronegative condition was 

 found to be no more effective than that in the electropositive condition, and it 

 is very probable that it has no scorching or fungicidal action at all, although 

 this could not be directly proved. 



Many experiments were conducted to determine whether the effectiveness of 

 copi)er fungicides could be increased by adding to them some substance which 

 increased their power of wetting the leaves, such as saponin, but the results were 

 negative. They did show, however, the danger of mixing any substances with 

 fungicides or insecticides without a nroper scientific examination of the changes 

 which they may bring about. Saponin in certain preparations was found to 

 entirely alter the nature of some copper compounds. Nicotin may be mixed with 

 Bordeaux paste without any detriment. 



The report concludes with an apiiendix by one of the authors on carbonates of 

 copper and the cuiiricarbonates ( E. S. K., 22, p. o04). 



The substitution of lime-sulphur preparations for Bordeaux mixture in 

 the treatment of apple diseases, W. M. Scott (U. -S'. /></*/. Ai/r., liur. I'loiit 

 liutufi, Ciix: o-'i, pp. lo, pin. J). — On account of the injury reported as due to 



