BROWN ROT OF SOLANACEAE. 



199 



Fig. no.* 



in steamed potato cultures, especially if the brown stain is well developed, and the well- 

 browned colonies on agar are usually dead. Two weeks is about the limit of vitality on 

 cooked potato; sometimes cultures were dead at the end of one week. An actively motile 

 bouillon-culture frozen in liquid air for 20 hours was still motile upon thawing out. Exam- 

 ined in a hanging drop within 20 minutes hundreds of the rods were active. This was not a 

 Brownian movement, but a rapid darting motion 

 which often carried the rods out of the field. 

 However, a distinctly less number seemed motile 

 than Ix-fore the exposure and poured plates (Vir- 

 ginia organism) demonstrated 50 per cent to be 

 dead. 



The organism grew well in acid bouillon 

 (+33, acid of beef juice), but less rapidly at first 

 than in nitrate bouillon (+15). After 3 months 

 the bouillon was stained brownish. There was 

 then an interrupted, dirty, gray-white pellicle, a 

 dirty, brownish-white precipitate, and numerous 

 small crystals. The Virginia organism did not 

 grow well on No. 602, a rather acid agar made 

 from the juice of sugar-beets diluted with water. 

 The Virginia organism after growing in peptonized 

 Uschinsky's solution for from 9 to 14 days had 

 developed no pellicle, rim, or pseudozoogloeae, but only a thin clouding, with a small 

 amount of brownish-white precipitate. 



Around the surface growth, in the agar in contact with the air, a white amorphous sub- 

 stance develops. This substance is finely granular 

 M under the microscope and dissolves in acetic acid. 



There appear to be many degrees of virulence, 

 and possibly there are several strainsof the organism. 

 ^^_iM RESUME OF SALIENT CHARACTERS. 



POSITIVE. 



Cause of a vascular disease in solanaceous 

 plants potato, tomato, egg-plant, etc. and from 

 recent studies by Honing and others it would seem 

 also of a disease in plants of several other families. 

 Short rod, often termo-like, motile, flagella polar; 

 organism in the plant often easily mistaken for a 

 coccus; dissolves middle lamella, cellulose (?); 

 plugs vessels, attacks phloem, forms numerous 

 closed cavities in parenchyma of hosts; causes pre- 

 mature development of adventive roots in tomato 

 stems. The feebly virulent strains induce slight 

 local enlargements ; surface colonies on agar rather 

 slow-growing, roundish, white at first, then brownish; clouds bouillon with formation of 

 numerous flocculent particles which accumulate in top layers; culture fluids containing 

 grape-sugar, fruit-sugar, or cane-sugar brown decidedly after some weeks; growth in acid 

 bouillon (+33, acid of beef-juice) is feeble at first in comparison with that in +15 bouillon, 



*Flc. 1 10. Drawing designed to show the clearing action of Batltrium solanacearum on milk (a sub-culture from 

 colony B. Florida potato): .4, tube of milk inoculated July 6, 1905, and drawn August 4; B, uninoculated check-tube. 

 A has become translucent slowly without a previous precipitation of the casein; B is opaque. 



fFlG. in. Gelatin stabs of Bacterium solanacearum (Virginia organism) after about 1 6 days at room temperature. 

 No liquefaction. Inoculated Feb. i, 1904. Photographed Feb. 18. 



Fig. III. t 



