207 
the wood. Perithecia ovate-conical, very black and superficial, about 4 mm. 
in diameter, clothed with very minute black bristles about 20-30 microns 
in length. 
Asci (p sp.) 8-10 x 65-70 microns. 
Spores 7-8.75 x 10-14 microns. 
Common on Fraxinus and Ostrya hear Bloomington, Ind. Found on 
decorticated wood and underneath loosened bark. 
ROSELLINIA AS A PARASITE. 
Unlike Hypoxyllon and Nummularia, Rosellinia is of great economic 
importance on account of several of its species being active parasites. 
Of the one hundred seventy species now described, at least eight are known 
to be injurious and destructive to living plants. No doubt many other 
species will be found to be parasitic when a more thorough study is made 
of them. The following is a brief account of some of the most destructive 
species : 
Rosellinia quercina Hart. Perithecia scattered, seated on a_ black 
mycelium, black globose, about 1 mm. in diameter. <Asci sub-cylindrical, 
eight spored, 8-10 x 160-170 microns. Spores brown, acute at both ends, 
6-7 x 28 microns. 
This species is called the oak root fungus, and attacks the roots of 
seedling oaks that are from one to three years old. The mycelium spreads 
rapidly through the ground from one plant to another and is especially 
destructive during warm, damp weather. This mycelial form was formerly 
referred to a special genus, Rhizoctonia. The effects of the fungus are 
first shown by the wilting and drying of the leaves hear the top, the lower 
ohes following in order until the whole plant is killed. If a seedling so 
affected is pulled up and the roots examined, a fine, thread-like mass of 
white mycelium will be found completely enveloping the roots. The tap 
root will have dark ovoid bodies about the size of a pin head where the 
lateral roots join. The tap root is often quite rotten where the mycelium 
has enveloped it, and especially in the neighborhood of the black tubers. 
Numerous black sclerotia are found on the surface of the dead roots. The 
strands of mycelium readily penetrate the young rootlets not yet protected 
by a layer of periderm and may kill the plant in from ten to fifteen days. 
Slender hyaline conidiospores are usually found near the base of the stem 
and on the adjoining soil. Later the perithecia are formed on the dense 
mass of mycelium covering the superficial roots. 
17 —4966 
