BULLETIN 231] 



WALNUT CULTURE IN CALIFORNIA. 



347 



tion band spreads over the entire surface of the potato slices. The 

 starch where growth has taken place fails to give normal starch reac- 

 tion when treated with iodine, but gives a reaction for grape sugar. 

 This fermentation band is quite a constant characteristic and usually 

 appears. When the organism is growing slowly and at a rather low 

 temperature, the fermentation band is more likely not to show. 



The organism lives for several months on potato cylinders, having 

 been found alive at the end of four months when growing at a temper- 

 ature of 15 to 18 C. In some cases the cultures die after three 

 months. In the old tubes the cultures are very viscid and much darker 

 in color, raw umber. (W. and N.) 



FIG. SS. Typical growth of Pseudomonas juglandis: left in glucose bouillon, right 



on potato. 



Fermentation Zone. Special attention was given to the study of this 

 fermentation zone. Early in the study it was found that this was a 

 varying characteristic, one that appeared constantly during the warm 

 weather of the spring and summer, but failed to appear during the 

 cooler winter weather. This point was tested experimentally by ster- 

 ilizing two series of five petri dishes, each containing slices of potato 

 heated at 110 C. in autoclave for fifteen minutes. These two series of 

 five plates each were inoculated at the same time and from the same 

 culture. Both series of cultures grew well. Series I at a temperature 

 of 12 to 15 C. This we did not vary for five days from 15 C. 

 Growth was as vigorous as in those at the higher temperature. No 



