16 BULLETIN 1727, U. S. DEPARTMENT OF AGRICULTURE. 
Halsted (23), Prillieux and Delacroix (39), Stoneman (50), Sheldon 
(46), Potebnia (88), Shear and Wood (45), and Eriksson (16). 
Potebnia gives an especially good description. 
Mycelium.—The mycelial characters vary greatly with age and 
substratum. At first the mycelium is colorless, thin walled, septate, 
and quite uniformly cylindrical. Many of the cells later increase in 
diameter about threefold and tend to become thick walled and dark 
brown in color, resembling intercalary chlamydospores. Oil drops 
are commonly present in old mycelium. In culture, the mycelium is 
first colorless, then pink, and finally black. In host tissue the pink 
coloration is sometimes seen, and the blackening is quite commonly 
produced in fruit lesions. The brown, thick-walled, large-celled 
mycelium occurs commonly in host tissue. 
Acervuli.—The mycelial filaments tend to aggregate at certain 
points, branch, intertwine, and send out a palisade layer of short 
colorless conidiophores. The extent of stromatal development pre- 
vious to sporulation varies greatly and is apparently greater in cul- 
ture than in host tissue. The color of this stromatic tissue is brown 
or black. 
Setex.—Scattered about among the conidiophores are the long 2-3. 
septate, brown, thick-walled bristles, or sete, varying in length 
from 90 to 120 uw and tapering toward a blunt point. The sete may 
be much longer under certain conditions. The number in each 
acervulus varies greatly and is given as high as 24 to 36 by Potebnia. 
S pores.—From the tips of the conidiophores the spores are budded 
off apically, one at a time, and pile up in a pink slimy heap on top 
of the acervulus. The spores are embedded in a sticky water- 
soluble matrix, and the heaps are often as high as the sete, the 
latter apparently serving as supports to’ hold the spore mass in 
place. The spores are one celled, hyaline, oblong or ovate-oblong, 
and slightly pointed at one end. Spores vary considerably in shape. 
Their size is about 13 to 19u by 4 to 6yu. Usually two or three 
vacuoles are present. The spores are pink in mass. 
Sclerotial bodies.—These are usually the result of the further de- 
velopment of the stromata or bases of the acervuli, in which the 
whole mass becomes considerably enlarged and black in color. The 
size of these sclerotial masses varies greatly, as does also the degree 
of their development. Sclerotial masses are formed abundantly in 
culture and in fruit lesions. Sheldon (46) describes these in detail. 
In culture the spore mass may dry down and remain as part of the 
protruding sclerotium. In fruit lesions the spores are washed away 
and only the black stroma remains, forming the black spots in the 
fruit lesions previously described. 
Appressoria.—Normally, a germinating spore on a firm or hard 
substratum forms an appressorium at the tip of each germ tube or 
