DISEASES OF PLANTS. 353 



surface of the leaves gives complete protection from P. viUcola, the author 

 states as the result of recent studies that such application does not decrease 

 sugar formation. A high degree of soil moisture rather disposes the plants to 

 attack, but the leaves are not so influenced by atmospheric dampness during 

 several days. 



Injury to grape leaves by addition of sulphur to Bordeaux mixture, A. 

 OsTEBWALDEB (Latidic. Jahrb. Schiceiz, 29 {1915), No. 1, pp. 28, 29). — It is 

 stated that in the hot summer of 1911 the addition of from 2 to 3 per cent of 

 sulphur to Bordeaux mixture used to spray grapevines caused a spotting or 

 killing of the leaves. This was very pronounced in southern exposures and 

 in general where the direct and reflected heat from the sun caused high tem- 

 peratures. The injury was attributed to the formation of sulphuric acid under 

 these circumstances. 



Similar injury resulted, with formation of corky areas on the fruits, in cases 

 where pulverized sulphur was applied after the use of Bordeaux mixture, and 

 this was similarly explained. 



Pythiacystis infection of deciduous nursery stock, Elizabeth H. Smith 

 {Abs. in Phytopathology, 5 {1915), No. 5, p. 291; Science, n. ser., 42 {1915), No. 

 1086, p. 580). — A dieback of young deciduous trees, which has occurred exten- 

 sively in northern California for several seasons, has been traced to a species 

 of Pythiacystis morphologically identical with P. citrophthora, first described 

 as causing a rot of lemons (E. S. R., 18, p. 344). 



Most of the root stock is apparently immune to this fungus, but above the 

 bud the bark is said to be affected, cankers being produced which often girdle 

 the tree and kill back the whole top. Profuse gumming follows canker forma- 

 tion. The fungus has been isolated from peach, almond, pear, and plum, and 

 the disease produced by inoculation in apple, pear, peach, almond, apricot, 

 prune, and cherry. Similar cankers have been produced by inoculation with 

 P. citrophthora isolated from lemon fruit 



A pythiaceous fungus has been isolated from almond cankers and success- 

 fully inoculated into almond, readily developing an oospore stage. This fungus 

 has different characters of growth from the original strain and a less degree 

 of pathogenicity, but it is believed that it will ultimately be placed in the same 

 species. 



Mottled leaf of Citrus species, J. T. Babbett {Abs. in Phytopathology, S 

 (1915), No. 5, p. 292; Science, n. ser., 42 {1915), No. 1086, p. 58i ) .—Attention 

 is called to the fact that no specific cause has as yet been discovered for 

 this disease, which is still classed as nonparasitic. Affected leaves contain 

 more startch than normally on account of defective translocation, and there is 

 apparently also an excess of nitrogen. It is stated that some relation appears 

 to have been discovered between fertilization with nitrate of soda without the 

 addition of vegetable material and mottled leaf, but the author considers that 

 this is probably not an effect of the materials used but of the soil conditions 

 produced, since in plats in which litxeral use of vegetable material had been 

 made no mottled leaf appeared. 



In connection with the discussion of this paper, F. S. Earle stated that there 

 are probably two distinct types of mottled leaf in Cuba and the Isle of Pines, 

 arising respectively from what is probably a specific disease of small roots and 

 from general unfavorable soil conditions. 



Citrus gummosis and melaxuma, H. S. Fawcett (Abs. in Phytopathology, 

 S {1915), No. 5, p. 293; Science, n. ser., 4Z {1915), No. 1086, p. 582).— A descrip- 

 tion Is given of the gummosis due to Pythiacystis citrophthora, and the 

 melaruma of walnuts which is caused by a fung\is thought to be a species of 

 Dothiorella, 



