1917] DISEASES OF PLANTS. 349 



tice, uamely, that of alternating the red clover crop witli sjiiufoin or trefoil, 

 either alone or mixed with Italian rye grass. 



[Ufra disease], G. P. Hectoe {Ann. Rpts. Expert Offs. Dept. Ayr., Benyul, 

 1915, p. H3). — Experiments at various points on the control of ufra disease of 

 rice are described. In one set of these, burning the stubble and turning the 

 soil several times controlled the disease completely, while in another set one 

 plat was slightly attacked after this treatment. It is considered improbable 

 that any variety of rice is immune, but some varieties seem to escape owing to 

 their ripening so early as to avoid violent attack. 



Resistance in tobacco to the root rot disease, J. Johnson {Phytopathology, 



6 (1916), No. 2, pp. 167-181, figs. 6). — The results of two years' experiments on 

 the relative resistance of selected strains of tobacco to the root rot caused by 

 Thielavia basicola are given. The experiments were carried on mainly in 

 Ontario and Wisconsin, the work in Canada being largely with the Burley type 

 of tobacco while that in Wisconsin was confined to cigar leaf selection. 



The author states that a strain of White Burley has been developed which 

 possesses a high degree of resistance. Strains of cigar leaf tobacco are known 

 to exist that are practically immune to root rot, but the quality of these types 

 is considered unsatisfactory. Selection breeding is thought to offer the most 

 promising field for investigation for control of this root rot disease. 



Host plants of Thielavia basicola, J. Johnson {U. S. Dept. Ayr., Jour. Ayr. 

 Research, 7 {1916), No. 6, pp. 289-300, pis. 2).— The results are given of an in- 

 vestigation of the host plants of this fungus, carried on at the Wisconsin 

 Experiment Station in cooperation with this Department. 



About 200 species of plants were grown on soil known to be infected with 

 T. basicolu, and under favorable conditions for the development of the fungus 

 the following families of plants were found to be attacked : Arallacefe, 

 Bignoniacese, Compositte, Convolvulacefe, Cruciferese, Cucurbitaceae, Hydro- 

 phyllacese, Leguminosae, Malvaceae, Orchidaceae, Oxalidaceae, Papaveraceac, 

 Polemoniaceae, Portulacese, Primulacese, Scrophulariacete, Solanace^e, and 

 Violaceae. Among the plants studied, the author added 66 species to the list 

 of known hosts of T. basicola, 28 of these being leginnes, 20 solanaceous plants, 



7 cucurbits, and 11 belonging to miscellaneous families. 



It is considered that a difference in the su.^ceptibility of the various species 

 exists, and where earlier investigators have been inclined to doubt the para- 

 sitism of the organism, it is believed that their infection experiments were car- 

 ried on with what are known to be imnmne or very resistant plants. Basing 

 his conclusion on evidence from nearly 100 species of plants infected with 

 T. basicola from tobacco, the author considers that there are no specialized 

 races of this fungus. 



Diseases of vegetables, I. C. Jaggek {West. N. T. Hort. Soc. Proc, 60 {1915), 

 pp. 14O-I47). — This is a discussion of experiences, chiefly with bacterial blight, 

 early blight, and late blight of celery ; club root of erucifers, due to slime mold ; 

 root knot of cucumbers, tomatoes, lettuce, and other greenhouse plants, due to 

 nematodes ; and onion smut. 



Cucumber mosaic disease, W. W. Gilbert {Phytopatholoyy, 6 {1916), No. 2, 

 pp. IJfS, 14-i, pl- 1)- — A brief outline is given of work in progress in investigat- 

 ing the mosaic disease of cucumbers, which is known to occur both la green- 

 houses and in fields. 



A new infectious mosaic disease of cucumber, S. P. Dooltttle {Phyto- 

 patholoyy, 6 {1916), No. 2, pp. 145-I47). — The author gives a description of field 

 observations and laboratory and field experiments on the cucumber mosaic 

 disease. 



