Mat 20, 1910] 



SCIENCE 



797 



During the following season at the same place the 

 disease was found to be as prevalent as it was 

 the year before. In some fields it caused the 

 death of at least 5-6 per cent, of the seedlings, 

 and, later in the season after a rainy spell, a large 

 percentage of the pods in contact with the ground 

 became infected. 



When diseased stems or pods were placed in a 

 moist chamber over night a fine moldy growth 

 surrounded them. Direct cultures made from the 

 stem gave a pure culture of a fungus, which, from 

 the character of mycelium and the production of 

 sclerotia, showed that it belonged to the form 

 genua Rhizoctonia. Interesting studies were made 

 of its growth on various media. Inoculation of 

 healthy plants grown in sterile soil resulted in the 

 production of lesions characteristic of the disease, 

 upon the inoculated plants, the checks remaining 

 healthy. Subsequently from these lesions the 

 fungus was again isolated and the characters of 

 its growth noted. Inoculations were also made on 

 healthy pods, in every ease resulting in a char- 

 acteristic Rhizoctonia canker. No perfect stage 

 has yet been observed. 



The writer is carrying on further experiments 

 with this organism and with a culture of Cor- 

 ticium vagum in an effort to discover whether 

 they are identical. Professor H. R. Fulton, for- 

 merly of the Louisiana Agricultural Experiment 

 Station, carried on a considerable number of in- 

 fection experiments during the summer of 1907 

 with a Rhizoctonia which he isolated from the 

 bean pod, and produced lesions on seedling beans 

 and on injured pods. 



Observations on Apple-tree Anthracn-ose : Pro- 

 fessor H. S. Jacksos^, Oregon Agricultural Col- 

 lege and Experiment Station. (Read by title.) 

 The Frog-eye Disease of Apple Leaves: Dr. John 

 L. Sheldon, University of West Virginia. 

 The history, cause and present distribution of 

 this destructive disease of apple foliage are re- 

 ferred to briefly. Several reasons are given why 

 it seems preferable to use the name " frog-eye " 

 for the disease of apple leaves caused by Illospo- 

 rium maUfoliorum, instead of the name "brown- 

 spot." (Specimens of the diseased leaves were 

 shown. ) 



The Ohio Outbreak of Fusarium Blight of Potato 

 in 1909: Professor A. D. Selbt, Ohio Agricul- 

 tural Experiment Station. (Read by title.) 

 On Mutualism in certain Parasitic Bacteria and 

 Fungi: Mr. Thos. F. Manns, Ohio Agricultural 

 Experiment Station. 



In artificially demonstrating the production of 

 disease, the writer believes that in the past too 

 little recognition has been given to the organisms 

 associated with the specific cause of the disease. 

 It seems quite probable that the intensity of the 

 disease, together with the varying symptoms, de- 

 pends quite largely upon the parts played by 

 others than the specific organism. In past experi- 

 mental work on disease production, we have pro- 

 ceeded by determining the specific organism and 

 eliminating all the associated organisms. The 

 writer believes that in the future, if we are to 

 know more concerning the progress of disease and 

 the cause of its virulence, we must take into 

 account the role played by the intimately asso- 

 ciated organisms. 



During the past two years the writer has been 

 working upon the blade blight or " red leaf " of 

 oats; a disease which experimentally is shown to 

 be due to bacteria. In this work two bacteria 

 were associated in the diseased blades. Inocula- 

 tion work with each of the organisms separately 

 showed that one was specific and capable of pro- 

 ducing limited lesions in the oat blade, while the 

 second organism produced no lesions at all; how- 

 ever, when both the organisms were inoculated 

 together as a mixture the typical oat blight 

 symptoms followed. After repeated demonstra- 

 tions with similar results, it was concluded that 

 we have in these two organisms a mutualism or 

 symbiosis in the production of this disease. 

 Platings from the inoculation of the two organ- 

 isms in mixture showed the presence of both the 

 organisms throughout the resulting lesions. The 

 writer has described the specific organism as 

 Pseudomonas avencB n. sp. and the associated 

 organism as Bacillus avenw n. sp. 



On artificial media considerable advantage was 

 noted in the growth and virulence of the specific 

 organism when grown with the associated or- 

 ganism. 



The writer believes there exists similar rela- 

 tionships among fungi in the production of disease, 

 however, in these cases, the associated organism 

 may be only a semiparasite, following closely on 

 the heels of the specific organism. It seems prob- 

 able also that such relationships as the latter may 

 exist between the speeilio fungus and certain 

 bacteria. 



Such relationship suggests itself as prevailing 

 between the Fusarium of potato wilt and a certain 

 Vermicularia which is so frequently associated in 

 culture work upon potatoes infected internally 



