DIMORPHISM IN CONIOTHYRIUM PIRINUM SHELDON^ 
C. H. Crabill 
Several years ago the writer began a study of the Phyllostictas 
and Coniothyriums associated with the frog-eye leaf spot of apple. 
In a previous paper^ the morphology, cultural features, and host 
relationships of Coniothyrium pirinum were briefly dealt with. The 
following report is the outcome of pure culture studies of C. pirinum 
isolated from apple leaf spots. 
The first cultures of this fungus, Strain I, were secured in 191 1 
from Black Ben Davis leaves at Blacksburg, Va. In 191 3 another 
strain. Strain II, was obtained from the same source. Although the 
mycelium, pycnidia and spores of the two are in no wise to be dis- 
tinguished from each other under the microscope, the two strains are 
readily distinguished when grown in Petri dish culture on artificial 
media. Starch agar^ has been used almost exclusively in these 
studies. Plates of this agar were poured, cooled, and inoculated at 
the center by the use of a platinum wire. Tubes of this medium were 
used in making dilution and stock cultures. 
Strain I, four years after isolation, exhibits the same characters 
as when first secured. It may be described as follows: 
Petri Dish Culture:^ Starch Agar 
Mycelium pure white or pinkish until about the loth day, acquiring 
then in spots, which spread gradually throughout, an olivaceous 
color. Pycnidia very few, large, multilocular, prolific, irregularly 
distributed about the point of inoculation, appearing 8 to 30 days 
after inoculation (Fig. i). 
Strain II when first isolated was described as follows: 
1 Paper No. 40 from the laboratories of Plant Pathology and Bacteriology, 
Va. Agr. Exp. Sta. 
2 Crabill, C. H. Studies on Phyllosticta and Coniothyrium occurring on apple 
foliage. Rep. Va. Agr. Exp. Sta. 95-115. 1911-12. 
3 Made according to the following formula: H2O, 900 cc; MgS04, .5 g.; K2HPO4, 
i.o; NaNOs, 2.0; KCl, .5; FeS04, .1; Agar agar, 20.0. Cook, filter, and while still 
hot add the following paste: H2O (cold), 100 cc; cornstarch, 10 g. ; and sterilize. 
4 Unless otherwise stated, cultures were incubated in moist chamber. 
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