DISEASES OF PLANTS. 847 



Infection experiments with parasitic fungi, IV, O. Treboux (Ann. My col., 

 12 (1914), No. 5, pp. 4S0-483) .—This is a continuation of studies previously 

 noted (E. S. R., 28, p. 844) regarding tlie habits and tendencies of several rust 

 fungi in connection with host plants. 



The 1914 outbreak of rust on winter grain in Bavaria, L. Hiltneb 

 (V/chnbl. Landw. Ycr. Bayern, 1914, No. 25; abs. in Internat. Inst. Agr. [Rorne^, 

 Mo. Bui. Agr. Intel, and Plant Diseases, 5 {1914), No. 8, p. 1091). — In parts of 

 Bavaria alarm was caused by rust on wheat and rye, due generally to Puccinia 

 glumarum, occasionally associated with P. triticina. The features of the out- 

 break are compared with those of a previous one. 



It is thought that the rust is less severe on fields properly nianurod, also on 

 thosg having a good even stand as compared with those having a thin stand. 



The true cause of severe outbreaks is held to be the weather, the outbreak 

 occurring after a number of hot days followed by frosts or heavy dews and cool 

 weather. Local quick-growing varieties were most severely attacked, other 

 varieties, especially pedigreed ones, remaining nearly free. Mist seems very 

 favorable to the spread of rust. The first reports of attack came from the 

 same place each year, confirming, it is held, the importance of atmospheric 

 factors. 



The cause and prevention of dry spot of oats, W. Kruger and G. Wimmer 

 {Ztschr. Ver. Deut. Zuckerindus., No. 704 (1914), II, pp. 707-758, pi. 1, figs. 

 12). — ^A description is given of this trouble, with an account of an extended 

 study thereon. It is claimed to be primarily physiological, due to the injurious 

 influence of residues of physiologically alkaline salts (in particular sodium 

 nitrate), and avoidable by altering the character of the soil as regards alka- 

 linity. This may have been increased in soils at first only slightly alkaline by 

 reactioas occurring in connection with commercial fertilizers employed, calcium 

 carbonate being significant in this connection. 



Suggestions made regarding the treatment of excessively limy soils include 

 the employment of iron chlorid, iron sulphate, or powdered sulphur, and the 

 use of green manure crops or stable manure. 



Experimental studies on the causes predisposing wheat to attack by 

 Erysiphe graminis, V.Rivera (RicercJie Sperimentali sulle Cause Predisponcnti 

 il Frumento alia " Nebbia.". Rome: R. Staz. Patol. Veg., 1915, pp. 42, figs. 4)- — 

 An account is given of studies on the germinability of the conidia of E. graminis 

 and the receptivity of wheat plants for the fungus as influenced by various 

 factors. 



It is stated that a condition predisposing the host to attack is diminution 

 of turgor, which may be due to dryness of the soil or to elevation of the temper- 

 ature of the air. Germination of the conidia, on the ther hand, is favored by 

 a state of moderate humidity and temperature. These facts may help to ex- 

 plain the contradictions in the claims made by investigators. The question 

 of susceptibility may reduce itself to a consideration of the relation between 

 cellular turgor in case of the fungus and epidermal tension on the part of the 

 host. The constitution of the cell sap and membranes as determined by nutri- 

 tional supply may be a further factor. 



A bibliography is appended. 



A new disease of germinating wheat, P. J. O'Gara (Science, n. ser., 42 

 (1915), No. 1079, pp. 313, 314).— The author reports having observed consider- 

 able unevenness of the stand in Utah wheat fields in April, 1915, there being 

 a large proportion of very weak plants. The fields were known to have been 

 infested in the previous year by the wheat straw worm, but a careful exami- 

 nation of the infected plants did not reveal the presence of the larv£E of this 

 insect. 



