10 Apkil, 1919.] Tomato Diseases. ' 233 



Dwarf varieties appear to be best able to resist attacks, the later planted 

 bushes are not so seriously aflFected. 



Experimental Work. 



A number of experiments have been carried out in various ways with 

 the sap expressed from diseased leaves ; others with fragments of diseased 

 leaves inserted in both stem and leaf. Portions of badly affected plants 

 have been placed on the terminal shoots of healthy plants, and kept 

 . under bell jars at temperatures varying from 30 deg. to 40 deg. C, and 

 in air having a heavy moisture content. A number of diseased terminal 

 leaves and stems were crushed to pulp, water was added, and the com- 

 bination filtered, and the filtrate mixed with soil in which young plants 

 were growing; diseased leaves were crushed, and the pulp placed in the 

 crowns of terminal shoots, some of which were pricked with a sterile 

 needle, and sap from diseased leaves sprayed over young plants. All 

 the plants, with the exception of two, were kept under bell jars, and 

 under conditions which were most favorable for the development of 

 either fungi or bacteria. 'No disease developed in any of the plants, and 

 the checks both under and out of the bell jars remained clean. 



The experiments and examination having failed to discover any 

 causal organism, specimens of diseased plants were forwarded to Dr. 

 Bull, Government Bacteriologist, and he also was unable to find any 

 organism connected with the trouble. Thus the several investigations 

 have thrown no light on the nature of the disease. Though the appear- 

 ance of affected plants to the naked eye, the symptoms, rapid develop- 

 ment of the discoloured areas, wilting and death of plants have all the 

 characteristics of a bacterial disease rather than one of a physiological 

 nature, fungi and bacteria are not present, or, at any rate, have not 

 been isolated. 



The Disease in Other Countries. 



Looking up literature dealing with diseases aifectiug the tomato in 

 various countries, I find that in the United States of America there is a 

 disease which so closely resembles the one under notice that in all 

 jirobability they are identical. 



Professor Selby (Bulletin 73, Ohio Agricultural Exp. Station) gives 

 tlie following description :— " An obscure disease of greenhouse tomatoes 

 caused much anxiety at the station in the spring of 1895. Specimens of 

 the same trouble have been received for examination ; it also reappeared 

 in 1896. This trouble shows itself as a general blighting of the plants 

 attacked, and exhibits much of the same symptoms as winter blight, 

 described in Bulletin 43 of the Experiment Station of Cornell University. 

 In the present case the younger leaves showed earliest indications of the 

 disease, and had a drooping appearance, with the leaflet turned inwards 

 at the margins, and occasional dead areas. The attacked leaves soon die, 

 and hang from the more or less drooping leaf stock. The thriftiest and 

 most vigorous plants were apparently as commonly attacked as the 

 others; the later plantings suffered most. The stems and leaf stalks of 

 the affected plants showed blackened, elongated spots upon them. In 

 the house where the trouble prevailed the green fruits were marked with 

 dark-brown irregular spots of varying diameter, . . . For this 

 blight no cause is at present assigned, and no organisms were found 

 associated with it." 



