1»20] DISEASES OF PLANTS. 847 



the problem, and It was found that evergreen plants partially smothered by 

 tif,'ht packing or prolonged mulch or snow cover during the winter are liable to 

 Injury from weakly parasitic fungi attacking the leaves. A number of organ- 

 isms have been ohtaiiied from such plants, among them liotrytis cimrca and a 

 dark sterile mold thus far unidentified. Observations and experiments have 

 shown that young plants, cutting off of roots, and prolonged smothering all 

 decrease the resistance, and that contact with the soil or dead organic matter 

 increases the likelihood of injury. Crowding the seedlings together or surfac- 

 ing the soil with gravel seems to result in decreasing loss slightly, probably 

 due to keeping the plants from intimate contact with the soil. Spraying and soil 

 treatment experiments with a number of fungicides have given no promise of 

 developing any disinfectant or protective treatment of practical value. 



Diseases of Illinois fruits, H. W. Andekson {Illinois Stu. Cirv. 241 (1920), 

 pp. S-155. pix. 2. fujs. 5S).— After giving an account of plant diseases in general 

 and an introductory chapter on the control of fruit diseases, the author de- 

 scribes the principal diseases occurring on fruits within the State and suggests 

 methods of control. Each disease is described and illustrated in such a manner 

 that It is hoped that growers will be able to recognize it when it is encountered. 

 Wlu'uever possible, the complete life history of the organism causing the disease 

 is given. 



The diseases enumerated are those attacking the apple, pear, quince, peach, 

 plum, cherry, raspberry, blackberry, dewberry, currant, gooseberry, grape, and 

 strawberry. 



Apple blotch control, W. S. Brock {Trans. Ind. Hort. Soc. 1918, pp. 103- 

 111, fly. 1). — Apple blotch, known in the South for 20 years, is said to be grad- 

 ually disseminating northward, 'being serious as far north as Greencastle, Ind., 

 and Champaign, 111. Treatments are discussed. 



The cause of bitter pit, A. J. Ewart {I'roc. Roy. Soc. Victoria, n. ser., 30 

 {1911), A'o. 1, pp. 15-20). — This is a review of the fourth report by McAlpiue 

 (K. S. R., 37, p. 455), also of contributions by others on the subject. The present 

 position in regard to bitter pit is summed up as regards the groups of facts 

 supporting the different theories, of which those based respectively on the 

 bursting of cells and on vascular interruptions are criticized, w^hile that based on 

 poisoning by sprays is favorably discussed. 



An undescribed apple spot {Kentucky Sta. Rpt. 1919, pt. 1, p. jp). — A brief 

 description is given of a form of injury to apples first noticed in 1019. 

 It is characterized by a depression of the surface of the fruit that may be either 

 very dark or normal green. The spots vary from 5 to 20 mm. in diameter. 

 Sections of deep green spots showed them to be from 5 to 8 mm. in diam- 

 eter and rather spherical in outline. Sometimes the centers of the spots 

 showed a brown area of dry, punky tissue. Where no discoloration was 

 observed, sections frequently revealed identical spots, but often 3 or 4 mm. below 

 the surface of the fruit, with perfectly normal tis-sue intervening. The dis- 

 eased tissues are said to be bitter in taste. Sections made of spots showed a 

 fungus constantly associated with their presence, and the greatest growth of 

 the fungus seemed to be just outside the zone of dense greenish cells, but not 

 extending more than 1 mm. into the healthy tissue surrounding the spot. 



Peach canker, W. A. McCubbin {Canada Expt. Farms Bui 37, 2. ser. {1918), 

 pp. 20, pis. 6, figs. 2). — The results are given of six years' investigation on the 

 cause and method of control of peach canker due to Valsa leuco,<itoma. This 

 fungus is said to establish itself in dead portions of trunks, twigs, etc., from 

 which it attacks the living tissue, stimulating the surrounding tissue into exces- 

 sive growth, so that a pronounced callus ring is formed around the canker. 



