STEWART'S DISEASE OF SWEET-CORN (MAIZE). 



135 



A ugusl 24, 1902. Inoculated. 



August 2g. All the cultures resemble each other closely. The potato out of the water is slightly to distinctly 

 grayed, and bears a thin, decidedly yellow slime. In one tube it was recorded as bright yellow. 



September. The potato-cylinders are grayed to a greater extent than they were and the organism is yellower in 

 some tubes than in others (variability in potato-cylinders). When compared with the check-tubes there is an incon- 

 spicuous pink tint in the potato (?). Repetitions in 1909 and 1913 (held 5 months) failed to give this tint. Fig. 64 

 shows appearance on potato contrasted with that of Bacterium campestre. 



On coconut cylinders Bad. stewarti made only a moderate amount of growth. Its 

 color was buff -yellow and crystals were formed. Repeated in 1913 the following results 

 were obtained : Moderate to good growth ; pale buff -yellow slime and precipitate ; no crys- 

 tals. In the milk of the coconut there was a moderate growth with yellow rim and precipi- 

 tate, and subsequently the fluid became yellow (checks remained colorless). When old 

 there was a copious yellow growth with a wide yellow rim; the fluid was pale yellow. 

 Though acid when inoculated it was now feebly alkaline. There were no crystals. 



On cylinders of yellow turnip there was a thin buff-yellow slightly iridescent growth. 

 At the end of a week this was decidedly less than in corresponding tubes of Bad. campestre. 

 Growth ceased, practically, after the second week. There was a buff-yellow precipitate in 

 the fluid surrounding the cylinders, but no thickening of the water with bacterial slime. 

 There was no browning or softening of the substratum. The 

 culture was alkaline to litmus at the end of the fifth and ninth 

 weeks. Repeated in 1913 with same results, except recorded as 

 not iridescent. When old the growth was orange-ochraceous, 

 feebly alkaline, wet-shining, not viscid, moderate in amount, 

 and free from crystals. 



The appearance of this organism when grown on rutabaga 

 was much the same as on yellow turnip. On the seventh day 

 the growth was about one-tenth as much as that of Bad. 

 hyacinthi and one-twentieth to one-thirtieth as much as that 

 of Bad. campestre. On the eighteenth day streak-cultures 

 yielded a thin buff-yellow growth covering the whole surface 

 exposed to the air ; this was not smooth and not dense enough 

 to hide the slight irregularities of the substratum. Its surface 

 was slightly iridescent, and when examined under the hand-lens 

 fine striae were visible. The water contained a moderate amount 

 of buff-yellow precipitate, but was not filled with a solid slime. 

 In old cultures there was no increased growth, no brown stain, and no softening of the 

 tissues. The iridescence persisted. The cultures were alkaline, at least after a time 

 (thirty-fourth and sixty-fourth days), and had a feeble, peculiar smell. On the thirty- 

 fourth day the thick slime would not wet litmus paper until water was added. 



When tried in 1913 on white turnip cylinders standing in water (stock 5778), there was 

 a moderate to good, pale yellow, flaky, iridescent surface growth, and a pale yellow precipi- 

 tate. When old the slime was ocher yellow, slightly alkaline, not viscid, wet-shining, not 

 copious, and free from crystals. 



On radish cylinders (tests of 19 13), there was a thin, whitish, iridescent surface growth 

 with a scanty yellowish precipitate and either no browning or slight. 



Steamed cylinders of sugar-beet standing in distilled water proved a very good medium 

 for Bad. stewarti. It grew on this substratum abundantly and without retardation. The 

 color of the growth on the cylinders was a deep buff-yellow, and there was a copious buff- 

 yellow precipitate in the fluid at the bottom of the tube. 



Fig. 64. 



*Fig. 64. Bacterium stewarti (a), and Bacterium campestre (b), after 30 days on cooked potato at room-temper- 

 ature. The former grew only during the first few days, ;'. e., was not able to use the starch as food ; the latter continued 

 to grow for weeks, owing to its diastasic action on starch. Bad. stewarti shows a little slime on the upper part of the 

 potato (dark part) and a small amount of precipitate in the water (at right). Bad. campestre has covered the potato 

 and filled the water solid. Photographed November 2, 1908. 



