1918.] mSEASES OF PLANTS. 649 



ing the least marked results. A striking feature of the plat treated with creo- 

 sote was its relative freedom from weeds throughout the season. 



Early and late blight of potatoes — cause and methods of control, J. Wood- 

 man {Tram. III. Hort. Soc, n. ser., 50 {1916), pp. 297-310) .—This address 

 deals with the causation and control of both early and late potato blights from 

 the standpoint of the potato grower, also briefly with Rhizoctonia and other in- 

 fluences affecting the potato industry. 



Odontia sacchari and O. saccharicola, n. spp., on sugar cane, E. A. Buet 

 {Ann. Missouri Bot. Gard., 4 {1917), No. 3, pp. 233-236, figs. 2).— Two new 

 species of Odontia, which have been collected by J. A. Stevenson, in Porto Rico, 

 and which are to be considered by him in a separate paper, are technically 

 described and have been named O. sacchari and 0. saccharicola. 



Mosaic disease of tobacco, G. H. Chapman {Massachusetts Sta. Bui. 175 

 {1917), pp. 72-117, pis. 5). — The results are given of several years' investigation 

 on the cause, occurrence, appearance, and methods of control of the well known 

 mosaic disease of tobacco. These experiments were begun in 1907, and some 

 of them have been repeated several times to confirm data regarding certain 

 disputed points. More than usual attention seems to have been given the bio- 

 chemical phases of the subject. 



As a result of the author's experiments, it is believed that the disease is 

 primarily induced by disturbance in the enzym activities and their relation to 

 each other, due to abnormal metabolism and not to any parasite. 



A series of experiments were conducted to test the claim of Lodewijks that 

 colored light can diminish or cure mosaic disease (E. S. R., 24, p. G4S). The 

 author found that the different colors have little or no effect on the causal 

 agent of the disease; but, in the case of the blue, there is a strong depression 

 of the macroscopic symptoms of the disease. 



In connection with the control experiments, it was found that on fields 

 where the mosaic disease is prevalent, the primary infection can usually be 

 traced to the seed bed, and that many healthy seedlings are infected by work- 

 men when setting the plants. It is estimated that about 80 per cent of the 

 infection occurs in this manner. By careful attention to sterilization of seed 

 beds and handling of plants at the time of transplanting, it is believed that a 

 large percentage of infection may be avoided. 



A black ret of apples, G. T. Spinks {Univ. Bristol, Ann. Rpt. Agr. and 

 Hort. Research Sta., 1916, pp. 2/f-26; Jour. Bath and West and Sotith. Counties 

 Soc, 5. ser., 11 {1916-17), pp. 153-155). — Having followed up the studies pre- 

 viously reported (E. S. R., 36, p. 750), the author describes the type of rot pro- 

 duced by Monilia fructigena in mature apples of different varieties, indicating 

 some irregularities which were observed. The mycelium grows chiefly between 

 the cells, but also occurs sometimes within. The kind of rot produced by M. 

 fructigena can not yet be correlated with any chemical or physical character of 

 the apple, but it is apparent that the factor which causes the black rot develops 

 only as the apple approaches maturity. 



As results of inoculation with M. cinerea were rather irregular, further ex- 

 perimentation is considered necessary. 



Apple leaf scorch, B. T. P. Babkeb and C. T. Gimingham {Univ. Bristol, 

 Ann. Rpt. Agr. and Hort. Research Sta., 1916, pp. 41-45; Jour. Bath and West 

 and South. Counties Soc., 5. ser., 11 {1916-17), pp. 167-171).— A. form of leaf 

 scorch of apples, occurring usually during the month of June, with complete 

 freedom of the leaves of the second growth, is described, with discussion of the 

 possible bearings of the various factors. Though the problem is still regarded 

 as unsolved, there is thought to be some ground for the belief that soil moisture 

 and temperature are in some way concerned. 



