COBB S DISEASE OF SUGAR-CANE. 



55 



fungus and one small whitish bacterial colony. Plate VI, nothing. Plate VII, nothing. Plate 

 VIII, 2 white colonies. Plate IX, nothing. 



The plates were now put into the incubator at 30 C. 



Eleventh day. Plate I, one large opaque yellow colony, and hundreds of small yellow colonies of 

 Bact.vasculanim. Apure 

 culture, with exception of 

 the large colony. Plate 

 II, one white colony and 

 hundreds of the Bad. vas- 

 cularum; a pure culture, 

 with exception of the one 

 white colony. Plate III, 

 a pure culture of Bad. 

 vascularum. Plate con- 

 tains several hundred 

 colonies and those which 

 have broken through to 

 the surface are circular, 

 quite transparent, and 1 

 to 5 mm. in diameter (fig. 

 31). Plate IV, hundreds 

 of colonies of Bad. vas- 

 cularum, a pure culture. 

 Plate V, one fungus 

 colony and one white bac- 

 terial colony; with these 

 exceptions a pure culture; 

 hundreds of minute yel- 

 low colonies of Bad. vas- 

 cularum. Plate VI, a 

 pure culture with at least 

 100 colonies, transfers. 

 Plate VII, a pure culture. 

 Plate VIII, same, with exception of two intruding colonies. Plate IX, a pure culture. 



Colonies on VII to IX too close together to estimate their number; 2,000 at least on each plate. 



The colonies appear sooner on plates made from young cultures. 



Fig. 25: 



Koomm 



mm 



Fig- 26. t Fig. 27.J Fig. 28 



The well-developed surface colonies in uncrowded agar plates are 4 to 6 mm. in diameter 

 (occasionally 8 mm.), pale-yellow, wet-shining, rather flat, with sharp margins and no dis- 

 tinct appearance of granulation under a hand-lens magnifying 6 times (fourteenth day). 



*Fig. 25. Cobb's disease of sugar-cane: Cross-section of a small bundle from an inoculated plant, showing the 

 bacteria, and red stain (the dark parts). Slide 299 A 2, lower left section. 



fFiG. 26. Bacterium vascularum: A detail from slide 310 (17; . e., from fig. 12, near location of micrometer scale. 



|Fig. 27. Bacterium vascularum: Detail from the cavity shown in fig. 23. 



Fig. 28. Flagella of Bacterium vascularum stained by the night-blue method. After R. Greig Smith. 



