246 EXPERIMENT STATION RECORD. [Vol.35 



No curative treatment is known. Preventive measures include the use oi' 

 stock and soil known to be free from the disease, selection of resistant 

 varieties, control of insect parasites, and care in cultural operations to prevent 

 injury to the plants and transference of the organism. 



Leaf scorch, scab, and gray mildew of cucumbers, O. Appel (Deut. Landw. 

 Presse, 42 (1915), No. 85, pp. 728, 729, pi. i).— This contains descriptions of 

 the respective effects on cucumber of Corynespora melonis, Cladosporium 

 cucumerinum, and Botrytis cinerea, with some discussion of conditions and 

 means of their communication. Control measures include the employment of 

 only sound seed with good cultural conditions, and destruction of diseased 

 plants. 



Control of Corynespora, the cause of leaf scorch of cucumbers, Obersteijm 

 {Illus. Schles. Monaischr. Obst, Gemiise m. Gartenbau, 4 {1915), No. 4, PP- 41-43, 

 figs. 2). — The author presents some information collected regarding the history, 

 effects, and control of the Corynespora disease of cucumbers, the control 

 measures including the avoidance of suspected soil, seed, or plant rubbish, and 

 disinfection of the seed bed with formalin. 



A physiolog'ical study of certain strains of Fusarium oxysporuni and F. 

 trichothecioides in their causal relation to tuber rot and wilt of Solanum 

 tuberosum, G. K. K. Link (Abs. in Science, n. ser., 43 (1916), No. 1105, p. 

 328). — The author states that certain strains of these two species of Fusarium 

 have produced both tuber rot and wilt of the Irish potato. Wilt is induced by 

 destruction of the root system and by clogging of the xylem elements in the 

 stem, and is, in mild cases, marked by such symptoms as discoloration of the 

 leaves, curling and rolling of the leaves, and production of aerial tubers. 

 Under field and storage conditions, F. oxysporum is said to be probably more 

 responsible for wilt than F. trichothecioides, while the latter species is more 

 responsible for tuber rotting. The optimum and maximum temperatures of 

 F. oxysporum are higher than those of F. trichothecioides. On the other hand, 

 F. trichothecioides gi-ows well at temperatures of 8 to 10° C. (46.4 to 50° F.), 

 while the other species does not. F. oxysporum is considered more cosmopoli- 

 tan, and it can utilize materials more readily than, but not so completely as, 

 does F. trichothecioides. 



Effect of certain species of Fusarium on the composition of the potato 

 tuber, L. A. Hawkins (U. S. Dept. Agr., Jour. Agr. Research, 6 (1913), No. 5, 

 pp. 183-196). — A report is given of an investigation made to determine the 

 effect of F. oxysporum and F. radicola on the sucrose, reducing sugar, starch, 

 I)entosan, galactan, and crude fiber content of the potato. 



It was found that these fungi reduced the content of sugar, both sucrose 

 and reducing sugar, pentosans, galactans, and dry matter. The starch and 

 methyl pentosans were apparently not affected appreciably and the crude fiber 

 content was not reduced. It was found that these two species of fungi secrete 

 sucrose, maltase, xylanase, and diastase, the last-mentioned enzym apparently 

 being incapable of acting on the ungelatinized potato starch. 



Late blight of potato, G. P. Dabnell-Smith and E. MacKinnon (Agr. Gaz. 

 N. S. Wales, 26 (1915), No. 8, pp. 673-678, pis. 2).— Late blight (Phytophthora 

 infestans), which became serious in New South Wales in 1909 and widespread 

 in 1910, is said to have been considerably decreased by the dry conditions 

 prevalent in Australia for some years past. The development of the fungus 

 and the progress of the disease are described. 



Experimental culture work is said to have shown that the fungus thrives 

 best at 60 to 70° F., no conidia forming at temperatures above 77°, and no 

 further growth of mycelium taking place above 88°. The conidia germinate 



