DISCOLORATION OF THE FOLIAGE. 483 



interior. Its presence may be detected by a brown 

 or black spot upon the leaf; and wherever it is 

 noticed, the leaf should be plucked oif and burnt. 



3. FuNGL (1) Ascomyces huUatus. This is a veg- 

 etable parasite attacking the leaves of the pear, and 

 causing shallow, brilliant spots. Another, much 

 like it, aiFects the leaves of the peach, and resem- 

 bles large blisters, which distort the foliage. It is 

 induced by cold weather in spring, and by want 

 of drainage. When the disease commences, the 

 foliage should be dusted on its under surface with 

 dry flour of sulphur, or syringed with water mixed 

 with sulphur and lime, as for the vine mildew 

 (^Berlieleif). 



(2) Ceratifes. Page 432. 



(3) Cladosporhmi dendriticimi. Page 431. 



4. Discoloration of the foliage — Chlorosis. In the 

 cells of growing vegetation are nitrogenous globules, 

 containing a substance called chlorophyll. This 

 takes various colors, but in leaves and new wood 

 is generally green. The deeper colored the foliage, 

 the richer it is in this substance. This shows that 

 the globules are larger, and therefore that the cells 

 containing it are more fully developed, active, and 

 vigorous. Some varieties of fruit are constitution- 

 ally remarkable for deep-colored foliage ; and such 

 are vigorous and healthy under almost any circum- 

 stances. 



