54 
28. The shape of the perithecium with its beak. What is 
the function of the beak? DRaw. 
29. Upon crushing the perithecium, the contents. 
30. Shape and size of asci; thickness of their walls. 
31. Shape and size of ascospores; number in each ascus; septate 
or nonseptate? . 
Make prawines of the perithecium, asci and ascospores. (If material 
is not sufficient see Bot. Gaz. 45:379 and pl. XI.) 
The ascospores are probably forcibly ejected from the perithecia, 
as most ascospores are, and thus they may readily be borne to the unfolding 
leaves and produce primary infection in the spring. That primary infec- 
tion is commonly initiated by ascospores is evidenced by the fact that leaves 
on the lower branches are usually the first to show the disease in the spring. 
From whatever source primary infection may result, a new mycelium 
is started near the veins of the young leaves. As the lesions enlarge 
the acervulus-type of fruit-body is formed. In the prepared sections 
of acervuli, OBSERVE :— : 
32. The aggregation of hyphe radiating from the base of the 
fruit-body. 
33. The chains of conidia cut-off from the ends of the conidio- 
phores. These form so abundantly that they pile up into balls or strings 
and are held together while dry by a gelatinous matrix. 
34. The individual conidia, as to shape and size. Compare 
with conidia from Myxosporium and Sporonema stages. 
Make DRAWINGS to show the structure of an acervulus in cross-section, 
including a portion of the adjacent leaf-tissue and the vegetative hyphae. 
Saprogenesis. When the leaves fall to the ground the mycelium 
spreads rapidly to all parts of the leaf and lives saprophytically forming 
more acervuli and, in moist situations, the pycnidia of the Sporonema 
stage. The perithecia begin their development after the mycelium has 
existed saprophytically for a time. The ascospores are mature by early 
spring. 
Secondary Cycles originate from the conidia developed in acervuli 
on the leaf- and petiole-lesions. It is suggested by some that the mycelium, 
extending down from the diseased petioles into the twigs, plays an 
important part in the infection of the current year’s twigs. This has not 
been proved, but it happens either in this way or by infection during the 
summer resulting from conidia. The infected twigs are not killed but 
develop normal buds which put out leaves the following spring. However, 
the mycelium in the twigs gains enough headway during the autumn 
and early spring to cause the death of the twigs at a time when the leaves 
are only partially developed. 
REPORT 
1. From what is known of the life-history of Gnomonia veneta 
(Sacc. and Speg.) Kleb., work out possible control-measures and give 
‘reasons for each step, based on the life-history of the pathogene. 
