Inclement Weather, Diseases, Etc. 



291 



This yellow color is owing to a want of tone in the cel- 

 lular tissue of the leaves, which want of tone suspends 

 their functions, and prevents the formation of chloro- 

 phyle, a green matter which imparts its color to the 

 tissues, under the influence of light. The cause of 

 this want of tone in the cellular tissue always proceeds 

 from a diseased state of the roots. It is for this reason 

 that jaundice makes its appearance when the roots are 

 in contact with stagnant dampness, which causes them 

 to rot, and when they are attacked by the larvas of cer- 

 tain insects. To combat this evil, then, we must re- 

 move its causes. 



Red Leaves. This second malady bears a certain 

 analogy to the preceding one. Nevertheless, it differs 

 from it, in the color of the leaves, which assume a more 

 or less deep red tint, as early as the month of July, and 



[FiG. 114.] Leaves Attacked hy Leprosy. 

 finally drop off. This change, which is almost always 



