ADAPTATION. 29 



Chlorosis manifests itself with as much intensity in the 

 south, where light is never defective, as in the south-west or 

 centre, where the sky is often cloudy, and vice versa. Again, 

 anybody may notice chlorotic vines side by side with green 

 vines, that is to say vines receiving the same quantity of 

 light. 



The reflexion of the rays of the sun by soils of light 

 colour (chalky soils of Dordogne, Blayais, etc.) cannot be 

 invoked here, as vines become yellow in the darkest soils, 

 such as the calcarous soil of the Charentes, Saumurois, 

 Poitou, etc. 



G Foe'x, in his remarkable study. ' The Causes of 

 Chlorosis in the Herbemont, ' ' showed that the cpage became 

 yellow, especially in cold (or sour) soils, in spring. The 

 experiments made by him, which we witnessed ourselves, and 

 the results obtained, show that a smaller or greater facility 

 of heating of the soil may increase or attenuate chlorosis. 

 Millardet and others arrived at almost the same conclusion. 



We must draw attention to the fact that the chalky soils 

 above-mentioned, as well as the red and jchreous soils of the 

 Charentes and the greves soils of Bourgogne, are all coloured 

 brown, or even dark red, and they are mellow, light, and 

 permeable, and absorb heat easily. The first of these, notably 

 during the summer, after a few sunny days, are burning; and 

 it is in these soils that vines become most yellow. On the 

 other hand, white, compact, and sour soils never bear yellow 

 vines. 



Finally, in measuring the temperature of different soils, 

 some in which vines become yellow, others in which they 

 remain constantly green, we have never been able to find 

 any difference. We must, therefore, conclude that the 

 coldness of soil has nothing to do with chlorosis. Yet the 

 probatory experiments of Foex and Millardet tend to prove 

 the contrary. We will show later on how a soil remaining 

 cold during a long period may, in certain cases, aggravate 

 this affection, and also that the deficiency of light, which 

 always accompanies an intensity of heat, acts in the same 

 way. 



Chlorosis and Climate. The non-success of American 

 vines in many soils has been attributed to the climate. The 

 American vines, it is said, are not yet acclimatized. Has 

 this assertion any value? Firstly, it seems strange that 

 such opinion may have been expressed when yellow and 



