57 
abundant in August and may develop in the same stroma with pycnidia. 
They bear spores called spermatia. (See Cornell Bul. 293, pl. III, fig. 19.) 
Their function is unknown but it is believed by some that they are vesti- 
gial male elements. Whether perithecia are produced in the old primary 
lesions is not certain. Pycnospores produced in these primary lesions 
may, however, winter over and new ones may possibly be formed, thus 
completing the primary cycle. (See Cornell Bul. 293:.325-326.) 
The Secondary Cycles, especially those initiated in the late summer 
differ from the primary chiefly in that they certainly give rise to the 
ascogenous structures which develop into perithecia the next spring. 
Pathogenesis. Until the first of August, pycnospores are produced 
in enormous numbers on the mummied berries. They are discharged with 
rain or dew and initiate secondary cycles. Other cycles follow in succes- 
sion as long as pycnospores are developed. After about August 1, 
pycnidial production ceases and instead there are developed in the lesions 
pycnidium-like bodies called pycnosclerotia. 
Study slides provided or Cornell Bul. 293, pl. IV. oBSERVE:— 
17. The absence of a central cavity and of spores. 
18. The parenchymatous character of not only the walls but 
of the entire fruit-body. 
19. Differences in the character of the central portion as con- 
trasted with the wall-structure. 
READ Cornell Bul. 293: 329. DRaw to show the structure of the pycno- 
sclerotium. 
Saprogenesis. With the death and shriveling of the tissues in the 
berry, the fungus continues its activities as a saprophyte. The develop- 
ment of the incipient perithecia (pycnosclerotia) is halted by winter but 
resumed in late spring. In the thin-walled parenchymatous-like center of 
the pycnosclerotium, asci are developed and matured. Study sections 
through mature perithecia and OBSERVE :-— 
20. The thick dark walls of the cells making up the wall of the 
perithecium; the mouth or ostiolum. 
21. The rather thick-walled asci; their shape, size and position 
in the perithecial cavity. 
22. The ascospores; number and arrangement in the ascus. 
DRAW to show the structure of the perithecium. The maturation 
and discharge of the ascospores completes the secondary cycle. 
Pathological Histology. The effect of Guignardia Bidwelli: on the 
tissues of its host is always necrotic. Study sections through leaf-, stem- 
or berry-lesions. OBSERVE :— 
23. The contrast between healthy and affected tissues; changes 
in color, and appearance of cell-walls and protoplasts in the diseased 
tissues. 
24. Which tissues in each organ appear to be most affected. 
Is there any evidence of an attempt by the host to stay the progress of the 
pathogene by the formation of cork-tissue about the lesion? 
25. The presence of mycelium; inter- or intracellular? Are 
haustoria present? 
pRaw to show the points brought out in the study of the histological 
effects. 
REPORT 
1. Discuss the relation of weather-conditions to the disease, 
keeping remedial measures in mind. 
