DISEASES OF PLANTS. 649 



Bordeaux mixture gave no appreciable immunity. The authors do not 

 consider this a genuine disease, but state that it is probably due to 

 low vitality and hindered growth, caused by excessive moisture. 



Brief notes are given on leaf blights of native trees. Among those 

 described are the following: Leaf blight of sycamore (Glcesporium ner- 

 visequum), leaf blight of butternut (G.juglandis), leaf spot of chestnut 

 (Septoria ochroleuca), and leaf spot of wild black cherry (IS. cerasina). 



A bacterial disease of beets, Prillieux and Delacroix ( Gompt. 

 Bend. Acad. Sci. Paris, 127 (1898), Wo. 6, pp. 338, 339).— For several 

 years there has been noticed in the north of France and in the vicinity 

 of Paris a disease of beets, to which the name "yellows" (jaunisse) 

 has been given. This disease seems to appear on soil where seed beets 

 have been grown, and makes its appearance between the 1st and 15th 

 of July. At first the leaves lose their normal turgescence, the petioles 

 become less rigid, and the tip of the leaf turns down. At the same 

 time the leaves become finely variegated green and white, as is the case 

 in the mosaic disease of tobacco. This appearance is more noticeable 

 by transmitted light, the discolored portions, especially in the young 

 leaves, being translucent. With the progress of the disease the dis- 

 colored spots coalesce and the leaf dries up; at this time the color 

 varies from yellow to gray. When plants are severely attacked the 

 roots do not increase much in size, although retaining their normal sugar 

 content, and the total loss of the crop is about 50 per cent. If the dis- 

 eased beets are planted for seed in the spring, the leaves which appear 

 will show the pathological characters which have been enumerated. 

 Under the microscope the diseased areas show great numbers of short, 

 curved bacteria, which rapidly render the liquid contents of the cell 

 turbid. The chlorophyll bodies of the cell are discolored and the gran- 

 ules in the cells become more refractive and are more apparent than in 

 sound leaves. When mother beets are attacked by the bacteria, not 

 only the leaves but the floral bracts and calyx are attacked, and it seems 

 probable that the bacteria are able to persist, probably in the state of 

 spores, in the fruit of the beet. 



Experiments have been conducted to test the artificial infection of 

 beets with this disease with marked success. Three rows of beets were 

 seeded in sterilized soil and transplanted to a soil in which beets had 

 not been grown. One row was watered with a diluted pure culture of 

 the bacteria and in a few days the characteristics of the disease 

 appeared, while the others remained absolutely unaffected. 



In the second experiment dried leaves from diseased plants were 

 powdered and mixed with the soil in the garden in April. Young beets 

 were transplanted to the soil and, except when planted in the soil receiv- 

 ing the powdered leaves, there was no appearance of disease. The 

 authors consider it established that this disease is due to bacteria, and 

 further study under the direction of the minister of agriculture is con- 

 templated. 



