326 Wisconsin Academy of Sciences, Arts, and Letters. 
influenced by nutrition, moisture, and temperature changes, but 
there is no evidence to indicate that such change of suppression 
is permanent. 
It may be possible to view the ascus as homologous to the ooblas- 
tema of the red algae, but the fusion of the auxiliary cell with the 
filament brings in a phase of development which is not eEisily har¬ 
monized with the development of the ascus in the Ascomycetes. 
Morphological Observations 
Venturia inaequalis (Cooke) Winter is an Ascomycete classi¬ 
fied as a Pyrenomycete. Lindau (Engler and Prantl) places it in 
the order Sphaeriales, family Pleosporaceae. Fries (1819) named 
the conidial stages of the organism Spilocoea pomi. Fuckel trans¬ 
ferred the fungus to the genus Fusicladium. Cooke (1866) de¬ 
scribed the stage in which asci are formed and named the organism 
Sphaerella inaequalis. Winter transferred the fungus to the 
genus Venturia naming it Venturia inaequalis. Aderhold (1897) 
connected the Fusicladium stage with the perithecial stage known 
as Venturia inaequalis by Winter and, not aware that Winter had 
transferred the organism, placed it in the genus Venturia naming 
it Venturia inaequalis (Cooke) Aderhold. 
Venturia inaequalis is parasitic on the fruit and leaves of species 
of Pyrus and produces conidia during the spring and summer. 
As the leaves die and fall to the ground the mycelium, which is 
almost lacking and exists chiefly under the cuticle, penetrates the 
leaf tissue and during November in Wisconsin perithecial forma¬ 
tion begins. The perithecium is not embedded in a stroma. The 
ascospores are found in March and April but do not ripen prepara¬ 
tory to discharge until May, discharge becoming active about the 
time the blossoms of the apple are opening. 
The fungus is saprophytic from the time the leaf falls until 
the perithecium is formed. It is not known if the mycelium con¬ 
tinues to function after the ascospores have been formed. 
The mycelium is septate and branches irregularly. The un¬ 
inucleate cells are from ten to forty microns in length and five to 
eight microns in diameter. The conidia are produced on eonidio- 
phores when the latter are from two to thirty microns in length. 
In cultures four or five conidia may be borne in a cluster at the 
apex of the conidiophore. As observed on the leaf only one coni- 
dium is borne at the apex of the conidiophores. As each coni- 
