326 OHIO EXPERIMENT STATION: BULLETIN 214 
within them spore-sacs of a nearly fixed number and each sac con- 
tains a fixed number of spores of definite form for each species. A 
great many fungi develop these ‘housed’? or protected forms 
during the dormant period, and indeed, spore development may 
proceed in the periods of lower temperature. 
With the perithecial or sporehouse form of wheat scab, (Gzbber- 
ella), the spore sacs are formed during the later summer, in our 
latitude, and these spore sacs disappear before midwinter. For each 
genus or species under study, peculiar time relations of development 
may be discovered. The perithecial or spore sac (acsigerous) form 
just described, or some comparable development of the spores under 
a definite cover-form, 
is viewed asa more or 
less ultimate stage in 
the development of the 
higher fungi— the 
summit in the cycle of 
their development. 
The rot of stone 
fruits, such as peach, 
plum, cherry and the 
like, is commonly 
known only in its 
conidial development 
Fig. 11. Section through a spore case (ferithecium), late 
winter stage of black-knot fungus, showing spore sacs (asc?) called Botrytis. Recent- 
within. Beside it, three asci containing winter spores or asco- : 
spores, eight in each sac, arranged in adefinite manner. Along ly Norton has discov- 
with these are thread-like hyphae known as paraphyses ered the Sclerotinia or 
ascigerous stage devel- 
oped from the mummy fruits in which the fungus lay dormant fora 
time awaiting spring or summer conditions. 
The bitter-rot of apple and its cycle of development not long 
since brought to light in Illinois, also shows the relation of the apple 
mummies, decayed by attacks of this anthracnose, to its survival. 
The fungus lives over in the old rotted fruits, acted upon by bitter- 
rot alone, which hang upon the trees. The fungus may also survive 
in branch cankers upon the tree adjacent to mummies of the bitter- 
rot. Inthese branch cankers the spore sac or perithecial stage of 
the fungus is developed. Upon the coming of warm showery 
weather about early June, new spores are produced from either 
mummies or cankers and new infection may occur upon the new 
fruits. The problem of the control of this disease, therefore involves 
a knowiedge of its manner of survival. 
