COBB'S DISEASE OF SUGAR-CANE. 67 



smooth, glistening, rather small, round, rather flat with sharp margins, no distinct appear- 

 ance of granulation , alkaline to moist litmus paper, not noticeably viscid, coming up slowly 

 at 25 C. (about 5 to 10 days when poured from cane) ; rods short, measuring on an average 

 0.4 X IM when stained, but sometimes plumper and also longer forms occur; single, in pairs 

 (mostly), fours, or eights, end to end; pseudozoogloeae ; motile, single polar flagellum; cap- 

 sules ( ?) ; stains fairly well by Gram (see negative) ; strictly aerobic (so far as known) ; 

 optimum temperature about 30 C.; growth retarded by temperature of 35 C.; thermal 

 death-point 49 to 50 C.; growth on +15 peptonized beef-agar inhibited by addition of 

 small amounts of vegetable acids; growth on potato-agar somewhat better than on beef- 

 agar ; scanty growth on litmus-lactose-agar, with slow but distinct bluing ; good growth on 

 neutral or slightly acid peptonized cane-juice gelatin, streaks slide down in characteristic 

 "tear-drop" formation; occasional very slight liquefaction of gelatin; fairly good growth 

 on steamed cylinders of susceptible varieties of sugar-cane ; growth on potato cylinders and 

 coconut-cylinders good but not copious, moderate graying of the potato cylinder, mostly 

 out of the water; scanty growth on steamed red table-beet cylinders; good growth on 

 steamed onion and cauliflower; fairly good growth on steamed carrot and turnip; +15 

 peptonized beef-bouillon moderately clouded, pellicle rarely observed, whitish rim some- 

 times formed, prismatic crystals often present; nitrate bouillon moderately clouded; good 

 growth in neutral bouillon and in slightly acid beef-bouillon ( + 25 Fuller's 

 scale) ; feeble growth in beef -bouillon titrating 20 Fuller's scale; feeble growth 

 in Dunham's solution, and in Uschinsky's solution (see negative) ; litmus milk 

 is blued, the milk remaining fluid and opaque; the organism can utilize aspa- 

 ragin and ammonium salts as nitrogen food ; it can obtain carbon from cane- Fig. 36.' 

 sugar, dextrose, fructose, and glycerin (?); grows best with saccharose or 

 fructose (RGS.) ; sodium chloride in amounts greater than i per cent inhibits growth ; 

 slight reducing action on cane-sugar (see negative); alkalies prohibit the multiplication 

 of the organism, but when the reaction is faintly acid growth is quick and luxuriant 

 (RGS.) ; the most suitable media are neutral or slightly acid, peptonized cane-juice gelatin, 

 beet-juice agar with addition of peptone and saccharose, litmus milk, and steamed potato. 

 It is sensitive to sunlight. Crystals occur on agar (fig. 38). Group No. 21(^.3332523. 



NEGATIVE. 



No spores ; no long chains or filaments ; no pellicle (usually) ; colonies not noticeably 

 viscid ; not pure white on any medium ; not red, nor orange ; no gas in any medium ; no reduc- 

 tion of nitrates to nitrites; no acids; no reduction of litmus (lactose-agar, milk) ; no precipi- 

 tation of the casein in litmus-milk cultures ; no liquefaction of gelatin (usually) ; no growth at 

 37.5 C.; no piling up of the slime in the water in potato-cultures, as in the case of yellow 

 organisms, such as Bacterium campestre and Bacterium phaseoli; no growth in Uschinsky's 

 solution (frequently) ; no growth in Cohn's solution ( ?) ; no growth in an atmosphere of car- 

 bon dioxide ; no clouding of closed end of fermentation tubes of peptone-water containing 

 grape-sugar, cane-sugar, milk-sugar, maltose, mannit, or glycerin. No growth (usually) on 

 steamed cylinders of resistant varieties of sugar-cane standing in distilled water. Organism 

 does not use potassium nitrate as nitrogen food. Does not stain by Gram's method (RGS.). 

 Does not use glycerin as carbon food (RGS.). Does not grow in peptonized beef-bouillon 

 with 1.5 per cent or more sodium chloride. Does not reduce cane-sugar, according to R. 

 Greig Smith. Does not brown agar. 



*Fic. 38. Crystals from an agar streak-culture of Bacterium vascularum. More than 200 appeared in some of the 

 tubes. Notes of March 7, 1902, and of February 1004. 



