476 Journal of Agricultural Research voi. iv, no. s 



many colonies have a denser margin which is- lighter colored than the 

 center. When older, the center is not always uniform in color. It may 

 have yellowish bands or mottlings and patches of the lighter margin 

 color in it. There is not always a definite light margin, and some colonies 

 seem quite uniform throughout. The colonies range from 3 to 5 mm. in 

 diameter. On agar stroke this mottling is present when the culture is 

 young, but disappears in both stroke and plate colony as they get older. 

 Inoculations have been made with the mottled colonies and those uni- 

 formly colored — that is, either cream-colored or bluish throughout. All 

 types are infectious. 



Using subcultures from single colonies, the disease was reproduced 

 with this organism by needle-prick inoculations four diflferent times (12 

 plants) and twice by spraying water suspensions of it on middle-aged 

 plants growing in the greenhouses (7 plants). Checks held under the 

 same condition of heat and moisture remained healthy. Reisolation 

 inoculations by means of needle pricks were also made, and these, too, 

 were successful. 



The organism is a bacterium,^ motile by means of from one to three 

 polar flagella; it is non-gas-forming in peptone water with the sugars and 

 alcohols tried (dextrose, lactose, saccharose, maltose, mannit, and 

 glycerin). It did not cloud the closed end in any of the fermentation 

 tubes, but it clouds beef bouillon -f 15 in less than 24 hours at 23° C. when 

 transfers are made from beef bouillon. In 10 days the bouillon has 

 become a lime-green color.^ The organism clears sterile milk in 15 days 

 wdthout coagulation, the cleared fluid becoming a pale turtle-green color. 

 It blues litmus milk and will grow in peptone-beef bouillon at tempera- 

 tures ranging from 1.5° to 34.5° C, though it will not grow in bouillon 

 at 36° C. The thermal death point lies between 48° and 49° C. It 

 grows well in Uschinsky's and Fermi's solutions, changing them to pale 

 Veronese green and water green in 3 to 5 days, but grows very faintly in 

 Cohn's solution. The organism liquefies gelatin slowly at 18.5° C, one- 

 half of the gelatin in test-tube cultures being liquefied in 10 days. On 

 potato cylinders it produces a fleeting dark blue-green color. This strik- 

 ing color reaction develops promptly and disappears on the sixth day or 

 earlier. It grows in bouillon over chloroform, tolerates malic, tartaric, 

 and citric acid (o.i to 0.2 per cent) added to neutral beef bouillon, but 

 will not grow in neutral beef bouillon containing 0.3 per cent of these 

 acids. It grows readily in neutral and in beef bouillon -|- 5, moderately in 

 — 10 and — 18, faintly in —20, but will not grow in —22 beef bouillon. 



The organism withstands a limited amount of drying. A drop of a 

 I -day-old bouillon culture smeared over sterile cover glasses and kept in 



1 This use of the genus Bacterium is in accordance with the system of classification proposed by Erwin 

 F. Smith in A/i Bacteria in Relation to Plant Diseases, v. i, p. 171- Washington, D. C, 1905. (Carne- 

 gie Inst. Wash. Pub. 27.) 



2 Ridgway, Robert. Color Standards and Color Nomenclature. 43 p., 53 col. pi. Washington, I). C, 



