1019] 



ZELLER AND SCHMITZ — MIXED CULTURES 



191 



out and away from the medium influenced by their own growth 

 metabolism than to grow towards a diffusion center, whether this 

 center contains nutritive or deleterious materials. This may 

 also be the condition produced in stale cultures. 



Thanks are due to the Missouri Botanical Garden for the 

 facilities of the library and the laboratories and to Dr. B. M. 

 Duggar for helpful co-operation. 



Graduate Laboratory, Missouri Botanical Garden. 



