175 
dissemination of the ascospore in early summer and primary infection 
the following spring, but of this nothing is known. 
_ Secondary Cycles may or may not occur. This point is not deter- 
mined. The ascospores germinate in water by budding or by the pro- 
trusion of a short germtube when placed on leaves of the host. Artificial 
inoculation of the host has never resulted in infection. (Read U. 5. Agr. 
Dep., Veg. Phys. and Path. Div. Bul. 20, bottom of 38 to 40.) copy 
figures from pl. IV, showing two types of spore-germination. 
Pathological Histology. ‘Study the prepared cross-sections of a dis- 
eased leaf. Select a place in the section where the diseased tissues may be 
compared with the normal. OBSERVE:— 
16. The increased thickness of the leaf in the diseased portion. 
To what is this due, increase in size, or number of cells (hypertrophy or 
hyperplasia) ? 
17. Which tissues are most affected, palisade or spongy paren- 
chyma? 
18. The affect on the number, shape and arrangement of the 
palisade-cells; chloroplastids and cell-walls (hypoplasia and metaplasia). 
per ia cells were attacked before they began to differentiate into palisade- 
19. The effect on the epidermal cells on the upper surface of the 
leaf; on the lower surface. 
Make a detailed pRrawinc showing comparatively the histological 
structure of the diseased and the normal portions of the leaf. 
REPORT 
1. Write a letter to a peach-grower, giving brief and current 
directions for controlling peach leaf-curl. 
