568 SCIENCE PROGRESS 



which has been definitely reported by Edgerton {Louis. Agr. 

 Exp.Sta. Bull., 164, 191 8) and Massey {New Jersey Agr. Exp. 

 Stat. Report, 40, 1920, 541), and which is doubtless a factor 

 concerned in the delayed leaf fall. Butler observed that the 

 heliotropic response of sprayed bean leaves was slower than 

 that of normal leaves, and ascribes this delay to the shading 

 effect. No qualitative differences could be found between the 

 light transmitted by Bordeaux mixtures of various copper- 

 lime ratios. Butler considers that the increased transpiration 

 rates following spraying (which, in common with Duggar and 

 Bonus, he found to occur at night) are to be attributed to the 

 reduction of heat radiation by the film of spray and the conse- 

 quent higher temperature of sprayed leaves. In short, all the 

 direct physiological influences of Bordeaux mixtures on the 

 plant may be attributed to the shading action of the film, 

 diminishing light in the day, and loss of heat at night. This 

 conclusion agrees with Ewert's and also in part with Clinton's 

 observations that maximum effect was obtained with sprays 

 giving a heavy sediment. Throughout the work there is no 

 attempt to ascribe any of the direct effects of Bordeaux to 

 any chemical action of the copper present, which is, after all, 

 the most natural constituent to suspect. In fact it has been 

 shown by Porchet that copper can never be detected in plants 

 sprayed with Bordeaux, whilst it is easy to demonstrate copper 

 in plants if copper salts are supplied to the roots. Copper, 

 therefore, does not penetrate the leaves, and the general con- 

 clusion of all investigators is that the physiological influence 

 of Bordeaux mixture on plants is capable of a physical inter- 

 pretation. 



References to Earlier Work on the Subject 



Aderhold, R., " Uber die Wirkungsweise der sogenannten Bordeaux- 



briihe (Kupferkalkbruhe)," Centralbl. Bakt., 1899. 5, 217-20, 254-71. 

 Bain, S. M., " The Action of Copper on Leaves," Tenn. Agr. Exp. Sta. Bull., 



1902, 5, No. 15. 

 Bayer, L., " Beitrage zur Pflanzenphysiologischen Bedeutung des Kupfers 



in der Bordeaux-briihe," Kdnigsberg, 1902. 

 Chuard, E., at Porchet, F., " Influence des composes cupriques sur les 



ph^nom^nes de maturation," Bull. Soc. Vand. Sci. Nat., 36, 71. 

 Clinton, G. P., " Spraying Potatoes in Dry Seasons," Ccmn. Agr. Exp. 



Sta. Rpt., 1909-10, 739-52. 

 EWERT, R., " Der wechselseitige Einfluss des lichtes und der Kupferkalk- 



briihe auf den Stoffwechsel den Pflanze," Landw. Jahrb., 1905, 24, 233-310. 

 EwERT, R., " Weitere Studien uber die physiologische und fungicide Wirkung 



der Kupferbruhen bei Krautigen Gewachsen und der Johannisbeere," 



Z. Pflanzenkr., 1912, 22. 257-85. 

 Lutman. " Some Studies on Bordeaux Mixture," Vermont. Agr. Exp. Sta. 



Bull.. 198, 1916. 

 Porchet, P.. " Action des sels de cuivre sur les v6g6taux," Bull. Soc. Vand. 



Sci. Nat., 1903, 39, 461-552. 

 Ruhland, W., "Zur Kenntniss der Wirkung des unloslichen basischen 



