1917] DISEASES OF PLANTS. 541 



experimental plats at SHmmervale during the seasons 1913-14 and 1914-15. De- 

 scriptive and otlier data regarding the cotton varieties employed are included. 



The root disease of sugar cane, due to Marasmius sacehari, was noted on one 

 estate in 1914, but the use of resistant varieties has in recent years helped to 

 lessen the amount of trouble from this source. Thielamopsis paradoxa ( T. etlm- 

 ceticus) was troublesome on some estates, experiment proving the necessity of 

 properly making up the Bordeaux mixture for use in this connection. Colleto- 

 trichum falcatum was not severe during the season. 



Late cottons were badly affected with black arm, angular leaf spot, and bac- 

 terial boll disease, all due to Bacterium malvacearum. Losses from anthracnose 

 {Glomerella gossypii) were comparatively slight. 



The Glceosporium dieback of cassava was again prevalent in some districts, 

 and some plants at Codrington suffered considerably from a bacterial leaf dis- 

 ease. Yams were affected by a blackening fungus on the stems and leaves, the 

 spore measurements of which agree closely with those of G. pestis. 



Grapes affected with anthracnose (O. ampclophagum) were noted, the stems 

 also being attacked. Leaves of grape growing in an unsuitable situation 

 showed the presence of vine rust ( Uredo vitis ) , also of a species of Cercospora, 

 possibly C. viticola. 



Young mango trees were attacked by G. mangiferw, which blackened the shoots 

 and portions of the young stems. Sorghum leaves showing rust were found to 

 bear Puccinia purpurea and the rust parasite Darluca flluni. A leaf spot as- 

 sociated with Glo'osporium sp. was observed to cause considerable injury to 

 Pithecolobium unguis-coti. Some palms of the genus Phoenix were found to be 

 affected with Graphiola phoenicis. 



Annual report for 1915 of the botanist, R. H. Biffen {Jour. Roy. Agr. Soc. 

 England, 76 {1915), pp. 309-313).— This report deals with tests of seeds; identi- 

 fication of weeds, grasses, and cereals ; rapelike sports among swedes and 

 cryptogamic plant diseases, these last including potato-leaf curl and tuber wet 

 rot ; a rust and a bacterial disease of mangold ; club root of swedes and cabbage ; 

 mildew in oats, vegetable marrow, and parsnips ; blindness in barley and wheat ; 

 wheat bunt ; alfalfa sickness ; mildew on apple, peach, and gooseberry ; pear scab ; 

 apple canker; plum silver leaf; Botrytis on lettuce; and minor diseases of 

 ornamental plants. 



Leptospharia culmifraga is claimed to produce brittleness of wheat stems near 

 the ground level. Sporidesmium solani varians appears to be somewhat com- 

 mon, causing a leaf spot of early potatoes, but to be controllable by the timely 

 use of Bordeaux mixture. 



Hydrogen ion concentration and natural immunity in plants, R. J. Wagneb 

 {Centbl. Bakt. [etc.}, 2. AM., U {1916), No. 2^-25, pp. 108-119, figs. 7).— A pre- 

 liminary account is given of studies with Sinnpis alba, Brassica oleifera, Semper- 

 vivum hausmannii, and Solanum tuberosum. 



It is stated that the variation of hydrogen ion concentration in plant tissues 

 is a phenomenon of reaction to the injection of pathogenic bacteria. The course 

 and end results are related to the susceptibility of the plant in question and to 

 the character of the disease as acute or chronic. 



Crown gall or plant cancer, C. O. Smith {Mo. Bui. Com. Hort. Gal., 5 {1916), 

 No. 6, pp. 201-211, figs. 3). — This is a somewhat general discussion of the now 

 almost world-wide crown gall organism. Bacterium tumefaciens, and its degree 

 of attack and other relations to the large number of plants which it can infect 

 either naturally or artificially. 



It is believed that the soils of California are often naturally infected with 

 the crown gall organism, especially in case of those that were formerly wooded 



