1. The colonies of Gloeosporium olivarum on peptone-salts agar plate containing different concentrations of sodium 2, 4-dichlorophenoxy acetate (2, 4-D), 2, 4, 5-trichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, 2-chlorophenoxyacetic acid, and 2-methylphenoxyacetic acid lose in general their circular outline as growth continues, and their margin becomes wavy and irregular. On the other hand, the colonies on the same medium containing 2-methylphenol, 2-chlorophenol, 2, 4-dichlorophenol, potassium α-naphthaleneacetate, and CuSO4 resembled the controls in the regularity of their periphery.
2. Morphological responses of Gloeosporium kaki, and Schizophyllum commune to 2, 4-D were similar to those of G. olivarum in showing irregularity of periphery, while those of Cochliobolus miyabeanus to the chemical were indistinguishable from the controls except for smaller size.
3. These results support the view of Brown and others who stated that such an irregularity of colonies is a characteristic of the "stalingtype" growth.