BROWN ROT OF SOLANACKAE. 



199 



Fig. 110/ 



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 before 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 pseudozoogloea?, 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 

 under the microscope and dissolves in acetic acid. 

 There appear to be many degrees of virulence, 

 and possibly there are several strains of the organism. 



RESUME OF SALIENT CHARACTERS. 

 POSITIVE. 



Cause of a vascular disease in solanaeeous 

 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. 

 vShort 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, 



lll.t 



*Fio. no. Drawing designed to show the clearing action of Bacterium solanacearum on milk (a sub-culture from 

 colony B, Florida potato): A, 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. 



fFic n 1. Gelatin stabs of Bacterium solanacearum (Virginia organism) after about 16 days at room temperature. 

 No liquefaction. Inoculated Feb. 2, 1904. Photographed Feb. iS. 



