DISEASES or PLANTS. 541 



A dangerous genus (Phytophthora), A. A. L. Rutgers {Teysmannia, 24 

 {1913), No. 10, pp. 626-632). — Discussing briefly the genus Phytophthora, the 

 author compiles in brief form the dates of discovery of 14 species and one 

 variety, naming hosts in connection therewith. 



Investigations on th,e control of disease in plants, R. H. Biffen {Jour. 

 Roy. Hort. Sac. [London], 89 (WIS), No. 2, pp. 318^20).— This paper, besides 

 giving a general discussion of plant diseases and their control, refers more par- 

 ticularly to the work of Biffen (E. S. R., 28, p. 147), Spinks (E. S. R., 29, p. 

 844), and Orton (E. S. R., 30, p. 331), dealing with immunity or susceptibility 

 as related to manuring and to heredity. 



The preparation and composition of lime-sulphur sprays, A. A. Ramsay 

 (Jour. Agr. Sci. [EnglamU, 6 (1914), No. 2, pp. 19Jf-201).— The author reports 

 a chemical study of lime-sulphur sprays in which an attempt was made to 

 determine the exact composition of the material as well as the most satis- 

 factory proportions of lime and sulphur. 



From his experiments it is claimed that the ratio of lime to sulphur should 

 be between 1 : 2 and 1 : 1.9, the exact ratio being, probably, 1 : 1.95. The solu- 

 tion of lime sulphur is said to consist of calcium hydroxyhydrosulphid, cal- 

 cium thiosulphate, and calcium sulphate, with sulphur held in solution. 



The preparation and use of lime-sulpliur mixture, L. Savastano (Prog. 

 Agr. et Vit. (Ed. VEst-Centre), 35 (1914), No. 4, pp. 109-113; R. Staz. Sper. 

 Agrum. e Frutticol. Acireale, Bol. 2 (1912), pp. 6). — It is claimed that a spray 

 mixtui'e composed of lime, sulphur, and water in the proportions by weight of 

 1 : 2 : 10, prepared according to the process here recommended and described 

 in detail, gives satisfactory results when used as either insecticide or fungi- 

 cide, being relatively inexpensive in comparison with Bordeaux mixture as 

 ordinarily employed. 



Further observations on the fungicidal action of Bordeaux mixtures, 

 B. T. P. Barker and C. T. Gimingham (Jour. Agr. 8ci. [England], 6 (1914), 

 No. 2, pp. 220-232). — In continuation of a previous report on Bordeaux mixture 

 (E. S. R., 25, p. 458) the authors review their work and reply to criticisms 

 of Pickering (E. S. R., 26, p. 853). They claim that subsequent investigations 

 more strongly confirm their previous opinion than before. 



From a study of seedlings and foliage in relation to Bordeaux mixture the 

 authors have come to the conclusion that living cells with readily permeable 

 walls of the unchanged cellulose type or its equivalent are able to produce 

 and absorb soluble copper from insoluble compounds, such as the basic sulphates. 

 The area over which a single cell can exert the solvent action is limited by 

 the size of the cell or by the quantity of the solvent diffusing from it. Groups 

 of cells acting together may cause action over a ■Rider area than isolated 

 cells acting singly. The fate of the organism is held to depend upon the 

 relation between the amount of soluble copper produced and absorbed and the 

 rate of growth of the organism. This is held to be a significant point in 

 connection with practical spraying, since it explains why at times there is 

 little check to the growth of a parasitic fungus after spraying. Cells with 

 impermeable walls possess no power of solvent action upon insoluble copper 

 compounds. It is held that under changed conditions cells with normally im- 

 permeable walls may become permeable and capable of action upon insoluble 

 copper compounds. This, it is believed, will explain the difference in behavior 

 of summer and autumn apple foliage. 



Studies of mechanical frost injuries, P. Soeatjee (Ztschr. Pflanzenkrank., 

 24 (1914), No. 2, pp. 65-76, pis. 3). — The author reports on further studies 

 (E. S. R., 30, p. 541) carried out with cereals as affected by cold and parasitic 

 fungi. Supporting conclusions by Voges (E. S. R., 29, p. 244), he states 



