DISEASES OF PLANTS. 847 



autumn, as soon as danger of renewed growth is past, usually early in Sep- 

 tember. Since perithecia form on the berries as early as May, it is important 

 to destroy all disoasod fruit as soon as possible. 



Studies in the physiology of parasitism. — I, The action of Botrytis cinerea, 

 W. Bkown (Ann. But. [Londou], 29 (IDlo), Au. 115, pp. 313-3^8).— This contri- 

 bution, the first of a series of studies now being carried out, is intended to 

 lead the way to a fuller understanding of the more highly specialized parasites. 



A method of preparing quickly and in practicable quantities a very powerful 

 extract from the germ tubes of B. cinerea is described in some detail, as pos- 

 sibly applicable to other studies along similar lines. 



It is stated that the extract shows two types of action on a plant cell, one 

 on the cell wall leading to disintegration of the tissue, another on the proto- 

 plast producing death at a late stage of the former process. The extract may 

 be deactivated by heating, mechanical agitation, or neutralization with alkali. 



It is thought that neither oxalic acid nor oxalates have any share in pro- 

 ducing the toxicity of the extract, and that any lethal substance present must 

 be of a colloidal nature. The only active substance in the extract appears to 

 be the enzym, which produces a macerating effect mainly by solution of the 

 middle lamella, and which causes also the lethal action of the extract. The 

 death of the cells is brought about presumably by its action, either directly on 

 the protoplasmic membrane or indirectly as a result of its action on the cell 

 walls. The ability of certain tissues to resist the action of the extract is de- 

 pendent upon the special properties of their cell walls. 



Perocid as a substitute for copper sulphate in combating' Peronospora of 

 grape stocks, F. Gvozuenovic (Ztsclir. Landw. Vcrsuchsw. Osterr., 18 {1015), 

 No. 1-2, pp. 11-28). — This is an account and discussion of tests made with Pero- 

 cid, a proprietary preparation to be used in the form of spray, paste, or powder 

 for the control of I'eronospora, and a comparison of the fungicidal values of 

 such preparations witli those of sprays in common use. 



The hibernation of the powdery mildew of the vine (Uncinula necator) in 

 Hvmgary, J. Ihos {Bordszati Lapok, 1,6 (1914), Nos. 50, jip. 703, 704; 51, pp. 712, 

 713; 52, pp. 728, 729, figs. S; ahs. in Intcrnat. Inst. Agr. \_Rome'\, Mo. Bui. Agr. 

 Intel, and Plant Diseases, 6 (1915), No. 2, p. S12). — The question as to how 

 powdery mildew of grape passes the winter is said to be still unanswered. 

 Istvanfti, in 1908, is said to have been the first to find the perithecia in 

 Hungary. 



The author observed considerable injury to grapes in the autumn of 1913. 

 A large number of leaves examined in November showed perithecia on the 

 mildew patches. The very abundant formation of these patches was thought 

 to be due to the great variations in climatic conditions in that year, the summer 

 being cool and wet and the autumn dry and warm. 



A banana disease in Cuba, J. R. Johnston (Estac. Expt. Agron. Cuba Circ. 

 ^7 (1915), pp. 1-9, pis. 7). — An account is given of the appearance, progress, and 

 effects of a disease of banana in Cuba, which is stated to cause heavy losses 

 in some districts and to threaten banana culture in this region. 



The discoloration, wilting, and rotting of the parts is described, also the 

 appearance of the stems in cross section, showing the relation thereto of the 

 fungus, which is found in connection with the vascular bundles. The varieties 

 which appear to be susceptible or resistant are indicated. The use of 0.2 per 

 cent corrosive sul)limate or other disinfectant is recommended, also removal of 

 affected plants by cutting close to the ground and the application of quicklime 

 to the stump. 



Marasmius perniciosus n. sp., the cause of the krulloten disease of cacao in 

 Surinam, G. Stahel (Dept. Landb. Surinanie Bui. 33 (1915), pp. 27+25-\-26, 



