204 



BACTERIOLOGICAL METHODS 



nature, occurring in the soil and in surface waters, and because 

 they very frequently comtaminate potato cultures, are known as 

 the potato group. They are spore forniing, which spores are 



Fig. 67.— Wild and pseudo-yeasts. A, S. pombe. (After Lindner); B, Torulce. 

 (After Pasteur); C, Mucor, (i) spores; (2) germinating spores and mycelium; D, S. 

 apiculatus; E, Mycoderma vini. — (After Bioletti.) 



remarkably resistant to heat, being able to withstand boiUng for 

 2 hr. Lafar maintains that they will resist the temperature of 

 streaming steam for 6 to 7 hr., thus making them the most re- 



