CHLOROSIS 



35 



Such diseased leaves, and sometimes also young shoots, first 

 change colour to a sickly greenish-yellow, and then assume a 

 clear yellow colour, finally becoming almost white and drying 

 up. The disease is of frequent occurrence and attacks 

 plants belonging to widely separated families. The disease 



Fig. 4. Two portions of a branch of a pear-tree damaged by hail. The 

 left-hand figure shows the injured side of the branch ; that on the right hand 

 shows the uninjured side. Half nat. size. 



has been studied in detail by Viala, as affecting the vine. 

 When once attacked, the branches, although yellow, do not 

 die at once, but produce leaves which remain small and are 

 of a yellow colour. The branches produced are numerous, 

 very short, slender, and bear only rudimentary leaves. If 

 the disease occurs during the flowering season, the colour of 



