36 AMERICAN VINES. 



Since we started studying chlorosis in French regions, we 

 have always seen the same phenomena take place intense 

 yellowing during wet springs, slight on the contrary during 

 dry springs, and .in both cases disappearance in July or 

 August. The same thing happens with American vines; 

 but as chlorosis is generally more intense, the recovery of the 

 green colour is not so complete; sometimes, even with certain 

 varieties, it does not reappear at all. In this case, therefore, 

 chlorosis seems to be in intimate relation with humidity, and 

 yet we have seen that humidity alone had no such action. 



How can we conciliate these apparently contradictory 

 facts? As previously said, carbonate of lime seems to 

 have a more noxious action on the vine when dissolved in 

 large quantities of water. The rain water, which is always 

 charged with carbonic acid, is its most active agent of disso- 

 lution, by infiltration in the soil, and the more abundant it 

 is, the more carbonate of lime in solution as bi-carbonate 

 will there be at the disposal of the plant, and consequently 

 the more intense the chlorosis will be. In June or July, 

 with the return of heat, the quantity of water contained in 

 the soil diminishes; a great quantity of bi-carbonate of lime 

 becomes insoluble again, and the chlorosis disappears.* 



However, chlorosis does not seem to be manifested in 

 direct relation with the percentage of water in the soil 

 estimated by weight, as is usually determined in physical 

 and mechanical analysis of soils. This is at least the result 

 of Houdaille and Mazade 's studies. It is the ratio between 

 the quantity of water contained in the soil and the volume 

 of the empty spaces existing between the particles of the 

 soil which it is important to consider, for it expresses more 

 accurately the state of saturation of the soil by rain water. 



One can then easily account for the differences shown in 

 the green parts of vines planted in soils containing the 

 same percentage of lime and in the same state. It is evi- 

 dently in places where water lies that vines will be the most 

 yellow. This is why the bottom of the valleys of calcareous 

 regions (Bourgogne, Charentes Aude, He>ault,) and places 

 where water springs naturally (surroundings of Vichy), 

 which seem at first appearance very favorable to American 



* It is easy to follow the progress of the dissolution and precipitation of the 

 carbonate of lime in the chalky soils of the Charentes. These soils, grey or 

 black, present during the drought, and, to a certain depth, numerous sinuous 

 white lines entangled like a network, which are deposits of pure carbonate of 

 lime in the drives formed by the roots of the vines. After heavy rains all these 

 lines disappear to reappear again with the drought. 



