656 EXPERIMENT STATION RECORD, [Vol. 37 



widely diffused and of considerable importance, but not so severe on clayey 

 and limy soils as on some others indicated. 



Anthracnose of Japanese persimmon, L. Maffei (Riv. Patol. Veg., 7 {1915), 

 No. 6, pp. 161-16S). — A brief description is given of a disease of fruits of 

 Japanese persimmon in the botanical garden at Pavia, caused by Olceosporium 

 kaki. 



Report of the plant physiologist, B. F. Floyd (Florida Sta. Rpt. 1916, pp. 

 30-50, figs. 6). — This report gives the results of a study of the toxic effect of cer- 

 tain organic chemicals on citrus and of injury to citrus trees by ground lime- 

 stone. 



Previous investigations (E. S. R., 29, p. 248) having shown that dleback of 

 citrus trees could be induced by organic nitrogenous fertilizers, the author 

 reports on experiments to test the action of vanillin on both citrus seedlings and 

 citrus cuttings. This orga-nic compound was added to nutrient solutions used at 

 various rates in the growth of seedlings, and. while marked injury to the roots 

 was produced, no gum, which is characteristic of the disease dleback, was 

 formed in grapefruit seedlings. With citrus cuttings vanillin produce<l no gum, 

 but, as no gum was formed in a series of experiments in which copper sulphate 

 was used, it is believed that the lack of gum formation in cuttings may have 

 been due to the absence of growth. 



The attention of the station having been called to apparent injury In a number 

 of groves where ground limestone had been applied, an investigation was made. 

 Pot experiments indicated that ground limestone can. under limited conditions, 

 induce injury to citrus trees, and that this injury shows itself by a frenching, 

 or chlorosis, of the foliage of the trees. 



Some cases of injury to citrus trees apparently induced by ground lime- 

 stone, B. F. Floyd (Florida Sta. Bui. ISl (1911), pp. 161-179, figs. 6).— This 

 bulletin is essentially a reprint from the article noted above, with suggestions 

 for the control of the injury. 



Report of the plant pathologist, H. E. Stevens (Florida Sta. Rpt. 1916. pp. 

 66-79, figs. 2). — The Investigations reported by the author have been continue<l 

 along about the same lines as previously. 



A number of citrus trees which had been treated for gummosis have been 

 kept under observation for three years (E. S. R., 33, p. 55), and many of the 

 active areas have healed following the treatment. A study is being made of 

 the fungus and bacterial flora associated with gummosis and several nrganisms 

 are under observation, among them Phomopsis citri and Diplndia natalensi-K, 

 to determine whether these fungi are active agents In producing the disease. 



Pruning experiments for the control of melanose have been continued with 

 some success, summer pruning giving very good results in reducing the amount 

 of injury. 



The author is continuing his Investigations on citrus canker, paying particu- 

 lar attention to laboratory studies of the organism, especially In relation to 

 soils. Pseitdomonas citri has been cultured in gterllized soil for more than a 

 year, and experiments have demonstrated that it grows readily on sterilized 

 soil under moist conditions. Soil cultures made in the spring of 1015 have 

 beeu kept under observation and in nearly every Instance the organism has 

 been found present. The infecte<:l soil has been applied to healthy citrus foliage 

 and in all cases canker infections have resulted. Tests have been made of field 

 soil collected under infected trees, and while in a majority of the tests there 

 were negative results, in a few Instances the presence of the organism was 

 e3tabllshe<l by Inoculation experiments. 



Brief descriptions are given of lightning injury to citrus trees, the lemon 

 brown rot fungus, citrus scab, withertip, and stem end rot. In connection with 



