NOTES AND ABSTRACTS. 



247 



In fungicides of the Bordeaux type the copper is insoluble at first, 

 but becomes gradually soluble later on ; and it is held that the dissolving 

 agent is usually and mainly, with the aid of moisture, the carbon 

 dioxide of the air (p. 11), and not often substances excreted by the 

 fungus itself or the leaves of the host plant (p. 106), while the action 

 of the fungicide is regarded as due in part to the permeation of the 

 leaves by the soluble copper, and in part to the coating of copper car- 

 bonate on the outside of the leaf (pp. 4 and 112). Better results are 

 obtained from substances insoluble to start with than from those con- 

 sisting of compounds of copper already in a soluble form (p. 181). It 

 is a fallacy, however, that the presence of any soluble copper in a spray 

 should be avoided (p. 7). 



The Woburn Bordeaux, the making of which was described in the 

 Eighth Eeport (p. 9), is now estimated to be twelve times as efficient 

 as ordinary Bordeaux (p. 59). The latter, when dry, is not satisfactory 

 as a substitute for a freshly prepared solution, but it is now possible to 

 obtain the Woburn mixture, or another basic sulphate analogous to 

 it, in the form of paste, and at a cost considerably less than that of the 

 copper sulphate alone which the grower would have to use to make 

 Bordeaux of the same efficiency in the ordinary way. This paste simply 

 requires mixing with water at the rate of about 15 pounds to 100 gallons 

 to reproduce a substance which, as regards the copper compound present 

 in it, is absolutely identical with that of a freshly-made preparation 

 (p. 183). 



In the making of ordinary Bordeaux the lime should be as weak as 

 possible (p. 50), any increase of this ingredient tending to delay and 

 diminish fungicidal action without materially reducing the risk of injury 

 when the scorching action of lime itself is taken into account (pp. 16 

 and 185). Experience is tending towards a reduction in the strength of 

 the mixture, the usual formula recommended now being 9^ pounds of 

 copper sulphate and the same amount of lime to 100 gallons of water 

 p. 185). The prevalent idea that Bordeaux does not begin to act for some 

 days after its apphcation has been disproved (p. 186), though the effects 

 may not become visible at once. The addition of treacle to the mixture 

 is not recommended, as it results in a liquid of very variable strength 

 (p. 80). Bordeaux mixtures should not be kept in tinned-iron vessels, 

 some, especially Woburn Bordeaux emulsion and paste, acting on these 

 metals and becoming rapidly decomposed (p. 48). Growers have in 

 many cases scorched the foliage of their trees by the use of Bordeaux 

 emulsion when sent out in tin canisters (p. 70). 



When buying a fungicide it should be remembered that its efficiency 

 is not to be estimated by the amount of copper contained in it, but by 

 the amount which becomes soluble and therefore available for fungi- 

 cidal action (p. 6). It is likewise irrational to judge of its value by the 

 amount of deposit left on the leaves. 



Numerous experiments on scorching and fungicidal action are 

 detailed in the report (p. 116 et seq.), and it has been found that the 

 scorching action of different salts of copper is independent of the nature 

 of the salt taken, and depends solely on the quantity of copper present 



