ROTS. 509 



and no spores observed; zoogloea in liquid cultures. Stains readily with aqueous 

 stains. Gram negative. 



It grows readily in the ordinary culture media. Upon potato, growth is charac- 

 teristic; at first light yellow, and in old cultures a golden brown, abundant, moist, 

 shining, slimy. Gelatin liquefied slowly. Litmus milk becomes slightly alkaline, 

 casein separated and gradually redissolved. On nutrient agar, translucent, yellow 

 slime. No gas from dextrose, lactose, etc. Uschinsky's solution, growth retarded and 

 feeble. Aerobic. Indol produced. Nitrates not reduced. Diastase produced. 

 Optimum temperature, 25 to 30; thermal death-point, 51.5. 



CONTROL. The removal of diseased leaves in the early stages has 

 been practiced by some growers with success, but care must be taken 

 not to remove so many that growth will be checked. Manure containing 

 diseased cabbage refuse must not be used. Seed disinfection with i :i,ooo 

 mercuric chloride, fifteen minutes, or formalin 1:200, twenty minutes, 

 is recommended. Rotation of crops, and planting on new land should 

 be practiced whenever possible. If practicable, the seed bed should be 

 made in sterilized soil, so that the plants will be healthy when set in the 

 field. 



WAKKER'S HYACINTH DISEASE. 

 Pseudomonas hyacinthi Wakker. 



HISTORY. One of the earliest landmarks in the study of bacterial 

 diseases of plants is the excellent contribution of Dr. J. H. Wakker,* a 

 Dutch botanist, who between 1883 and 1888 published five papers on 

 a disease of the hyacinth, caused by Ps. hyacinthi. Erwin F. Smithf has 

 carried the investigation farther and has described the causal organism 

 more fully. The disease was first observed in the Netherlands where it 

 frequently causes serious losses in the hyacinth gardens. It is not known 

 to occur in any other part of the world. 



SYMPTOMS. The disease is characterized by a yellow striping of 

 the green leaves and the bright yellow slime produced in the vascular 

 bundles of the bulb. The infection in the leaf spreads slowly to the bulb 

 by the multiplication of bacteria in the vascular system, filling the vessels, 

 especially those of the bulb, with a bright yellow bacterial slime. In 

 time, the walls of the vessels are destroyed and large cavities are formed 



* Wakker: Bot. Centralbl., 1883, 14, p. 315; Archives neerlandaises des sci. ex. et naturelles, 

 Tome XXIII, pp. 18-20. 



f Smith, Erwin P., " Wakker's Hyacinth Germ," Bui. No. 26, U. S. Dept. Agr., Div. Veg. 

 Phys. and Path, 1901. 



