MORPHOGENESIS IN VERTICILLIUM: A SELF‐INDUCED, NON‐HEREDITARY VARIATION IN COLONY FORM

Some homokaryotic isolates of Verticillium albo‐atrum (microsclerotial form) vary radically in colony appearance even when temperature, lighting, humidity and medium content are held constant. This variation is so great that it may easily be mistaken for hereditary variation. The environmental factors which control the variation are differences in shape of medium on which the colonies grow and presence or absence of other Verticillium colonies. The cause of the variation appears to be a diffusible substance which Verticillium itself produces.