DIMORPHISM IN CONIOTHYRIUM PIRINUM SHELDON 467 
In two weeks the spots inoculated with each strain turned whitish 
and bore several pycnidia from which it was easy to reisolate the 
strain. The cultures show that both the strains retained their diag- 
nostic characteristics. One month after inoculation no enlargement 
of the seared spots has taken place. In fact some of the dead tissue 
bearing pycnidia of the fungus has fallen out producing a "shot hole" 
effect. This is further evidence that Coniothyrium pirinum is a 
saprophyte. The above experiment was conducted under controlled 
conditions in the greenhouse. 
Conclusions 
1. Coniothyrium pirinum is sometimes dimorphic in culture and 
probably also in nature. 
2. Two distinct strains have been isolated, viz., a plus strain, which 
fruits abundantly, and a minus strain, which fruits poorly. 
3. The minus strain arises in artificial culture by sudden sporting 
from the plus strain. This phenomenon has been observed in four 
separate instances. 
4. Minus strains never give rise to plus strains but remain constant, 
generation after generation. 
5. Attempts to develop the strains from each other by continuous 
selection of extremes have been unsuccessful. 
6. Attempts to determine the cause of the sporting have been 
fruitless. 
Virginia Agricultural Experiment Station, 
Blacksburg, Va. 
