34 



appears in potato cultures of I^s. ccunpestris and Pa. pJia^eolL In 

 comparison with either of these species the growth of Ps. Jiyacintld on 

 potato lags far behind, e. g., at the end of 2 days at 20° to 25° C. it is 

 not one-twentieth as much, and at the end of 2 weeks it is not one one- 

 hundredth as much. After the second week the hyacinth germ shows 

 very little increase of growth on potato, whereas the other two germs 

 continue to multiply for many days, converting the fluid in the bottom 

 of the tubes into a solid mass of yellow slime even when as much as 2 

 or 3 c. c. of water is present (see Tafel YI, fig. 4, Centralb. f. Bakt., 2 

 Abt., Bd. III). This feeble growth on potato serves as a ready means 

 of distinguishing this organism from the cabbage germ and the bean 

 parasite, but not from some other 3'ellow bacteria, e. g., Ps. steivarti. 



The surface of this yellow growth, in Ps. hyacinthi even after several 

 weeks, is usually homogeneous, smooth, and wet-shining. Very rarely, 

 after the third week, I have seen a shagreen surface on the extreme 

 upper part of the potato cylinder. After a few weeks (3 to 4) the 

 bacterial layer is slightly sticky, often stringing up 1 to 2 centimeters 

 when touched with the loop. After 3 or i weeks, when a considerable 

 portion of the bacterial kwer may be presumed to Vje dead, pale yellow, 

 smooth, shining colonies, 1 to 3 mm. in diameter and gradualh' rounded 

 up from the margin to a rather thick center, are sometimes seen dot- 

 ting the surface. Zooglce^e occur in this slime, at least after some 

 weeks (30, 37 days), even when they are not visible in the form of 

 shagreen. In one culture which was examined microscopically in 

 water on the thirtieth day the}^ consisted of numerous tiny ragged 

 aggregates of 10 to 100 or more individual rods. 



All the cooked potatoes I have ever tested have been feebly acid to 

 litmus. This acidity is overcome by the growth of Ps. /ii/acH}t/u\ the 

 fluid first changing to feebly alkaline, and then becoming and remain- 

 ing strongly alkaline (13, 22, 21, 30, 37, 56, 67 days). 



The substratum out of the water is changed (as happens in case of 

 many other bacteria) to a pale gray within a few days, and this color 

 extends downward slowly into that part under the water, until after 

 3 or 4: weeks all is grayed; usually by the eighth or ninth day the 

 gray color extended down under the water 1 centimeter. This color 

 is a pale smoke gray, lightei- than Ridgway's smoke gray (1-12). 

 Its depth of color varies in different cultures, depending apparently 

 on slight chemical differences m the potatoes used. The fluid in the 

 bottom of these tubes remained free from color for a time, but after 

 3 or 4: weeks it became feebly browned. This brown color was distinct 

 enough to be detected without check tubes, but it was never more 

 than a weak stain (67 days). 



The cylinders were firm and resistant between the fingers, even after 

 the hyacinth organism had grown on them for 6 or 8 weeks, and their 

 cellulose was certainl}- not acted upon to any marked degree. The 



