DISEASES OF PLANTS. 44t 



mildew (M. ahii), scab (Fusicladium cffutmui), leaf blotch (Ccrcosponi Jiul- 

 ^tcdii), rosette, and dieback on pecans. 



Report of assistant plant physiologist, B. F, Floyd (Florida Sta, Kpt. 1909, 

 pp. LXIIl-LXXVIII, figs. 16). — The resnlts of experiments on overfertilizatiou 

 with cottou-seed meal, blood and bone, and dried blood as one of the canses of 

 dieback of citrus trees indicate that the disease is aggravated by maximum 

 fertilization with certain forms of fertilizers. The greatest detrimental effect 

 was noticed with nitrate of soda. 



Observations on yellow spotting of citrus leaves show that it is widely dis- 

 tributed throughout Florida, while its prevalence and severity vary consider- 

 ably in different groves in the same locality. The disease is not confined to any 

 particular variety of citrus trees, but is most evident on the grapefruit. No 

 cause has been found for the disease, and no remedies for its control are 

 suggested. 



The gross and microscopical appearances of chlorosis of cassava are given. 

 The cause apparently is a physiological one due to unfavorable soil conditions, 

 and may be avoided by planting upon rich soil where conditions are most 

 favorable to growth. 



Mutualism in certain parasitic bacteria and fungi, T. F. Manns (Abs. in 

 Science, n. ser., 31 {1910), No. 80d, pp. 797, 796'). — A synopsis is given of the 

 results of investigations on a disease of oats which has been experimentally 

 shown to be due to two species of bacteria (E. S. R., 22, p. 453). 



The author believes there exist similar relationships among fungi in the pro- 

 duction of disease, in which the associated organism maj' be only semiparasitic, 

 following closely on the specific cause of the disease. Such relationship, he 

 thinks, occurs between the Fusarium of potato wilt and certain species of 

 Termicularia, and ex])eriments are now in progress to determine this fact. 



Two barley blights, with comparison of species of Helminthosporium upon 

 cereals, L. H. Pammel, Charlotte M. King, and A. L. Bakke (loica 8ta. Bui. 

 116, pp. 17S-190, figs. //). — The results are reported of investigations on the 

 yellow leaf disease of barley (H. gramincum), which was prevalent in some 

 barley fields at Ames, Iowa, appearing just before the heading of the grain, 

 and on late blight {H. sativum), which manifested itself in the form of brown- 

 ish, circular, dark-colored spots, soon causing the leaves to become brown, and 

 also occurring upon the glumes and spikelets. 



This late barley blight, which did much damage, is the most serious barley 

 disease of Iowa, and is apparently transmitted with the seed. 



The bulletin closes with a discussion of the described diseases on barley 

 due to species of Helminthosporium and a list of the species of Helminthospo- 

 rium found on Graminejie and their characters. 



Bhizoctonia stem, rot of beans, M. F. Barrus (Ahs. in Science, n. sen, 31 

 {1910), No. 803, pp. 796, 797). — While working on bean diseases in the vicinity 

 of Oneida. X. Y., during the summer of lOOS, the author observed a large num- 

 ber of plants affected with cankers on the parts of the stems below or at the 

 surface of the ground. During the following season at the same place the 

 disease was found as prevalent as the year before. An examination of dis- 

 eased stems or pods placed in moist chambers showed the characteristic 

 mj'celium and the sclerotia of Khizoctonia. Inoculations of healthy potls re- 

 sulted in the production of the characteristic cankers. As yet no perfect stage 

 of the fungus has been observed. 



The author is carrying on experiments with this organism and with a cul- 

 ture of Corticium vagum in an endeavor to discover whether they are not 

 identical. 



