DISEASES OF PLANTS. 649 



red currants were infected, but gooseberries seemed almost entirely free from 

 the trouble. The only explanation offered for the freedom of the gooseberries 

 which is considered tenable is that of biological specialization. 



Note on. American gooseberry mildew, M. A. Bailey {Ann. Appl. Biol., 2 

 (1915), No. 2-3, pp. 162-165). — An instance is given in which gooseberry seed- 

 lings showing heavy infection during 1912 were, after removal to another area 

 where they, were left unpruned and where they were apparently favored by the 

 direction of the wind and the presence of a low hedge, almost entirely free from 

 the disease in 1913 and 1914. 



The South African mulberry blight (Bacterium mori), Ethel M. Doidge 

 (Ann. Appl. Biol., 2 (1915), No. 2-3, pp. 113-121,, pis. 6).— A report is given on 

 a study since 19U8 of a twig and leaf blight of black mulberry, which is rather 

 widespread in certain districts of South Africa. The organism has been isolated 

 and numerous infections have been obtained from pure cultures. 



The morphological and cultural characters of the organism corresponded 

 closely with those of B. mori causing blight of French and American mulberry. 

 The only important difference was that the organism causing the South African 

 blight has from one to four polar flagella as compared with one or two shown by 

 the American form. 



Spraying with Bordeaux mixture proved useless as a means of control. 



A brief bibliography is appended. 



Citrus canker in the Gulf Coast country, with notes on the extent of 

 citrus culture in the localities visited, E. W. Bergeb (Proc. Fla. State Hort. 

 Soc, 27 (1914), pp. 120-127; abs. in Mycol. Centhl., 5 (1915), No. 6, pp. 287, 

 288). — An account is given of a search for the origin of citrus canker after its 

 discovery in two widely separated localities in Florida. The disease is claimed 

 to have been found in Alabama, Mississippi, Louisiana, and Texas, but not at 

 Matamoras, Mexico. The original infection is thought to have come on speci- 

 mens from Japan, being probably mistaken for scab (Cladosporium citri). 



A list is given of varieties of citrus plants attacked, in the order of observed 

 severity. 



Citrus mildew, T. Fetch (Phytopathology, 5 (1915), No. 6, pp. 350-352). — 

 In a publication by Carter (E. S. R., 34, p. 447), attention was called to a mildew 

 of tangerine which, the author believed, had not been previously reported. In 

 the present paper, attention is called to the fact that mildew of citrus trees is 

 very common in Ceylon and also in India. It is considered one of the worst 

 diseases of citrus in Ceylon, where it occurs on varieties of sweet orange and 

 mandarin and is especially destructive on pomelo. 



Black neck or wilt disease of asters, W. Robinson (Ann. Appl. Biol., 2 

 (1915), No. 2-3, pp. 125-137, pis. 2).— Reporting results of studies since 1914 

 on the black neck or blackleg disease which is prevalent in market gardens 

 around Manchester, England, the author states that the tissues of the plants, 

 which may become diseased at any stage of growth, always contain the my- 

 celium of a species of Phytophthora, which, on isolation and reinoculation, 

 reproduces the disease. Tests with a Fusarium also isolated gave negative 

 results. 



It is stated that while some of the characters of P. omnivora ai-e shown, a 

 proliferation of the sporangium as here observed seems to be peculiar to this 

 species. No sexual structures have yet been observed. 



A serious disease in forest nurseries caused by Peridermium filamentosum, 

 J. R. Weir and E. E. Hubert (U. S. Dept. Agr., Jour. Agr. Research, 5 (1916), 

 No. 17, pp. 781-785). — The authors report P. filamentosum as causing a serious 

 di.sease of yellow pine seedlings at the Savenac nursery at Haugan, Mont. The 

 fact that the same species of Peridermium attacks both the lodgepole pine and 



