79 
13. The structure of pycnidial walls and conidia-bearing struc- 
tures. a 
Make a detailed prawine of the pycnidium and adjacent host-cells. 
The pathogene produces only sterile pycnidia on the leaves. Apparently 
on these organs the cycle is never completed. The pycnospores, matured 
in primary lesions on twigs and fruits, serve to initiate secondary cycles 
on all susceptible host-organs. In the twig-lesions, the pathogene hiber- 
nates either as immature pycnidia(?) or as mycelium from which pycnidia 
are developed in the spring. Thus is the cycle completed without the 
appearance of a sexual spore-form. 
Saprogenesis. There is no marked tendency exhibited by this 
pathogene to grow and develop saprophytically. It may feed to some 
extent on the dead tissues after leaves and fruit have fallen. The forma- 
tion of spore-producing pycnidia only during the fore part of the season, 
followed by the development (in the later secondary cycles at least) of 
pycnosclerotia, suggests that perithecia, similar to those known for Guig- 
nardia Bidwellit on grapes, may be produced during saprogenesis. They 
are as yet unrecorded. 
Secondary Cycles originate from the pycnospore-crop of the pri- 
mary infections. They are initiated only during the first half of the sum- 
mer, and probably do not often initiate other secondary cycles. They 
duplicate in all respects the primary cycles. 
REPORT 
1. Compare and contrast in parallel columns the two diseases 
of the apple:—blotch and sooty blotch. 
