420 Bulletin 76. 



ditions may be held responsible for their appearance. When we 

 come to the origin of grape shelling, the same causes do not ap- 

 pear, and meteorological influences seem to assume but a second- 

 ary position. 



Apoplexie, or Folletag e ."^ — These are the names applied to a 

 phenomenon which generally appears in July or August in vine- 

 yards, especially in those growing on deep and rich soils, which 

 previously showed no signs of disease. Upon isolated plants, or 

 sometimes upon entire portions of a vineyard, there suddenly ap- 

 pear leaves which have lost their lustre, and their natural turges- 

 cence ; in consequence they wilt and perish. The shoots dry from 

 above downward, and soon the entire plant dies. The trouble 

 however, is not always so severe as to cause the death of the plant. 

 One portion only of the plant may be affected and the remainder 

 be apparently healthy. But the shock to the plant is always 

 severe, and generally the effects of such an attack are beyond 

 perfect repair. The explanation which Leclerc givesf is as fol- 

 lows : " The rainfall during the year has been very heavy and 

 thus prevented the rapid heating of the soil and also caused the 

 atmosphere to be saturated with the vapor of water. In addition, 

 the skies of Touraine have been almost constantly overcast. The 

 growth of the vines was made, one might almost say, in the shade, 

 and under these circumstances the tissues of the plant have not 

 acquired the powers of resistance which they would have had if 

 the sun had shone ofteuer. The tissues were gorged with water ; 

 the evaporation from the plant was slow in consequence of the 

 humid condition of the air. The experiments of Sachs show that 

 transpiration (evaporation) increases as the temperature of the 

 soil is raised. Consequently the passage of water through the 

 roots and the wood must have been slow and a certain balance 

 was established between it and the process of transpiration. 

 Let us suppose, now, that suddenly the burning rays of the sun 

 strike the well developed foliage of the vines. The air is warmed, 

 dried more and more as the temperature increases, and with the 

 increased heat and dryness of the air the evaporation of the plant 

 becomes more energetic. Since the water lost from the leaves 



*G. Foex, Cours Complet de Viticulture, 1891, p. 466 et seq. 

 flbid. p, 467. 



