Mayis. I9IS Potato-Scab Organism 133 



found that no such involution forms were produced when the potassium 

 monophosphate alone was excluded, but they invariably appeared if it 

 . was present.^ / 



SUMMARY 



(i) Temperatures from 35° to 40° C. are most favorable for the ger- 

 mination of the gonidia of the potato-scab organism. They are unfa- 

 vorable for long-continued growth, although at 35° a stimulating effect 

 was produced at first. 



(2) The maximum temperature for growth is about 40.5°, the optimum 

 25° to 30°, and the minimum about 5° C. 



(3) Involution forms are produced, but not as the result of tempera- 

 ture conditions. They appeared abundantly when 0.25 per cent of 

 potassium monophosphate was included in a synthetic culture medium. 



' Miinter observed similar involution fonns in pure cultures of certain soil-inhabiting Actinomyces, 

 but on a somewhat different synthetic medium than that used by the writer. Among the species studied 

 hy MiinteT Actinomyces ckromogenes is mentioned. (Miinter, F. Uber Actinomyceten des Bodcns. In 

 Centbl. Bakt. [etc.], Abt. 2, Bd. 36, No. 15/18, p. 380-381. 1913-) 



