PLATE XXXVII 



Fig. I . — Lenticel in ripe fruit of Sapa plum. The walls of the cells lining the cavity- 

 give the staining reaction of cellulose. X 400. 



Fig. 2. — Lenticel in ripe fruit of Gold plum partially filled with parenchymatous 

 cells. Infection may take place through a lenticel of this type. X 400. 



Fig. 3. — Lenticel in green Burkank plum. The cell walls lining the cavity give 

 the staining reaction of cork. Infection may take place through a lenticel of this 

 type, but only in the manner shown in Plate XXXVIII, figures 1,3, and 5. X 400. 



Fig. 4. — Lenticel in green fruit of B X W21 completely filled with parenchymatous 

 tissue. Infection can not take place through a lenticel of this type. X 400. 



Fig. 5. — Ripe healthy tissue of Sapa plum, showing middle lamella completely 

 dissolved out owing to ripening process. This is the condition found in the ripe fruits 

 of the susceptible varieties. X 60. 



Fig. 6. — Ripe healthy tissue of Reagan plum two weeks after picking. The middle 

 lamella is still intact. This is the condition found in the ripe fruit of resistant varie- 

 ties. X 60. 



(396) 



