SCHUSTER'S GERMAN POTATO ROT. 



275 



exposed to normal conditions in a hothouse it is not parasitic. I could not get any infec- 

 tions either by rubbing it into stomata or by needle- puncture into leaves or stems. The 

 organism grows in milk about as described, but on agar streaks ( + 15) I did not obtain the 

 cross-folds and am inclined to regard this as an accidental phenomenon due to dry agar or 

 to some other peculiarity of medium. The organism was tried on various sugars and alcohols 

 in the presence of river-water and Witte's peptone (i per cent). Contrary to Schuster, it 

 ferments grape-sugar and galactose with production of an acid, but a similar solution with 

 cane-sugar gave an alkaline reaction (fermentation tubes, 11 days). The same results 

 were obtained in two repe- 

 titions (twenty-eighth day 

 and later) . The other car- 

 bon foods tested in fermen- 

 tation tubes were fructose, 

 lactose, maltose, mannit, 

 and glycerin. All of these 

 gave an alkaline reaction 

 (eleventh day). In two 

 repetitions the same result 

 was obtained after longer 

 periods. There was no gas 

 formation and no clouding 

 in the closed end. As 

 stated, the organism did not 

 rot potato tubers at 37C., 

 nor could we get any evi- 

 dence of growth above 34 

 C. in + 15 peptone-bouillon 

 or on steamed potato. It 

 grew better at 30 C. than 

 at 34 C. but less well than 

 at26C. It grows at i C. 

 Its thermal death-point is 



51 C., approximately. It 

 grows in bouillon over chlo- 

 roform without retarda- 

 tion. It grows in +15 

 peptone-bouillon with 4 

 per cent sodium chloride 

 and slowly with 5 per cent, 

 but not with 6 per cent. It 

 does not grow in Cohn's 

 solution. It grew in pep- 

 tone bouillon from 30 to +25. It grew about as well in 15 and 30 as in o or +25. 

 It grew well in Uschinsky's solution, forming a copious pellicle and after a time a pale 

 green fluorescence. f It is sensitive to dry air (dead on cover slips at end of 4 days). 

 It liquefied gelatin in the manner described by Schuster but did not liquefy Loeffler's 

 blood-serum, although it grew well upon it. It is quite sensitive to sunlight. 



Fig. 135.* 



*Flc. 135. Potato tubers inoculated with Schuster's Bacterium xanthofhlorum and exposed for six days to the dry 

 air of the laboratory at 27 C. Photographed Sept. 1 1, 1912, after slicing to show the very slight rot. The specks in 

 the rotted part are needle-punctures. In right lower figure there is rot in vascular ring at top near the pricks. 



fMiss Clara Jamieson isolated from Bad. xanthochlorum a non-fluorescent strain which retained this characteristic 

 in subcultures on various media as long as studied (some months). On agar-plates the non-fluorescent colonies looked 

 exactly like the fluorescent ones. 



