56 
Life-history. This pathogene exhibits in its life-history all the typical 
spore-forms and pathological phenomena of a large number of the leaf- 
spotting pyrenomycetes. ; 
‘ Primary Cycles are initiated in late spring and throughout the summer 
(Cornell Bul. 293: 310). The fungus winters largely in the mummies 
which lie on the ground or cling to the vines. (Note in the latter connec- 
tion, photograph 6.) Canes and tendrils may also harbor it. 
Pathogenesis. Some of the mummies are provided for study. 
With a hand-lens, OBSERVE :— : 
9. The presence of very numerous elevations,—the perithecia of 
Guignardia Bidwellii; the ostiolum at the apex. ; ; 
With the hand-lens and needle remove one or more of these perithecia 
(from the soaked mummy provided) to a drop of water on a slide; cover 
and examine with the lower-power, exerting slight pressure on the cover- 
glass. NOTE:— 
10. That if the perithecia are mature, the asci with ascospores 
will be forced out. 
11. The average number of asci in the perithecia; the number 
of spores in an ascus. 
DRAW an ascus with ascospores. These ascospores constitute in most 
seasons the chief inoculum for primary cycles. Discharged from the 
perithecia during rainy weather, they are blown by the breeze or splashed 
by rain-drops to young leaves or berries where they germinate and the 
germtubes penetrate the host-tissues. copy Cornell Bul. 293, pl. V, fig. 
28-29. Note the appressorium formed on the end of the germtube. 
Pycnospores overwintered in canes and tendrils may also serve to 
initiate primary cycles. (See Cornell Bul. 293: 326.) With hand-lens 
and needle, remove a few pycnidia from one of the cane-lesions. Crush 
on a slide in water or potassium hydroxide and study. MAKE OUT:— 
12. The numerous pycnospores set free from the broken pycnidia. 
Their form, size and color as compared with the ascospores. DRAW. 
These germinate by a simple germtube and infect young leaves and fruits. 
copy Cornell Bul. 293, pl. V, fig. 34. 
After penetration by the germtube of the ascospore or pycnospore, 
mycelium is slowly developed in the surrounding tissue. The first evi- 
dences of infection appear in one to three weeks, depending on 
conditions of the host and the weather. After the appearance of the 
lesions, the pycnidia develop (see photographs 1, 3, 4, 7 and 8) and form 
pycnospores with great rapidity. Study prepared slides provided and 
OBSERVE :— 
13. Position of the pycnidium in relation to the host-tissues. 
14. The pseudoparenchymatous wall of the fruit-body. 
15. The short conidiophores bearing the pycnospores; their 
origin and arrangement in the pycnidium. 
16. The ostioum through which the pycnospores are discharged. 
They are discharged by the pressure resulting from water-absorption 
by the gelatinous substance in which they are surrounded. These initiate 
the secondary cycles. 
Make a DRAWING to show the structure of the pycnidium and its rela- 
tion to the host-tissues. 
Saprogenesis. The fungus lives saprophytically after the lesion 
is fully developed until the following spring. From July until October 
certain fruit-bodies, known as spermagonia, are developed. They are 
