236 
half a centimeter or more. In the early stages of development in the spe- 
cies described the stromata may be lightly colored, but when the sporidia 
are mature the color of the fertile layer is black. Sometimes the substrat- 
um is stained by the fungus. One species is readily recognized by the 
characteristic orange color imparted to the wood beneath the stromata. 
Another species gives a peculiar ring-like marking to both wood and bark. 
If a stroma be cut through, the flask-like perithecia are found deeply 
embedded in it. They are arranged in a single row and open by minute 
pores (ostiola) on the upper side of the stroma. ‘The ostiola in some spe- 
cies may be rather promineutly raised giving the fertile surface a pimpled 
appearance, or they may be sunken; while in some forms they may be so 
obscure as to be passed over unnoticed. The edges of the stromata are 
usually sterile. 
The perithecia contain many eight-spored asci. ‘These asci are cylin- 
drical in shape and bear the spores in a single row. ‘They are readily dis- 
tinguished from the paraphyses with which they are found by their shorter 
length and the spores which they contain. 
The spores of the Nummularias vary greatly in size, color, and shape. 
The largest ones that the author has observed were about 16 microns long 
and one-half as broad, while the smallest were about 5 microns long 
and about 24 microns wide. 
The shape varies from elliptical to orbicular. When the spores are 
young they are usually hyaline, but as they become older, they turn brown 
and in some species they finally become opaque. 
In general, the Indiana species of Nummularia are saprophytic in 
habit and consequently have but little economic importance. Under cer- 
tain conditions, however, V. discreta* becomes parasitic and causes consid- 
crable damage to poorly kept apple trees. To many fruit growers it is 
known merely as apple canker; others distinguish it as the blister canker. 
The fungus gains a footing in a wound or in a decayed portion of the tree 
and spreads to the living parts. The stromata arise upon the mycelia be- 
neath the epidermis of the host. The overlying epidermis shortly becomes 
dry and papery and sooner or later it is torn and drops away leaving the 
*Canker of Apple—Hasselbring, Ill. Exp. Sta. Bull. 70. 
Fungous Diseases of Plants—Duggar, pp. 282-284. 
Apple Blister Canker and Methods of Treatment—W. O. Gloyer, Ohio xp. Sta. Cir, 125. 
The New York Apple Tree Canker. Bulls. N. Y. Ag. Ex. Sta. Nos. 1f3 and 185. Paddock. 
The Control of Canker in the Orchard—J. R. Cooper, Neb. Hort., Vol. 3, 1913. 
