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A NEW FUNGUS DISEASE 

 OF THE YAM. 



By 

 Seiya Ito, Nogakushi. 



In the vicinity of Sapporo, the leaves and vines of the cultivated yam (Dios- 

 Gorea Batatas) are yearly more or less affected by a fungus, belonging- to the genus 

 Cylindrosporium. The same fungus is also found on the wild yam (Dioscorea ja- 

 •ponica). 



The disease of the wild yam was first noticed in 1889 by Prof. Dr. K. 

 MiYAKE in Tokvo, and after that time, many specimens of the diseased yum both 

 cultivated and wild were collected in various places of our country by him and 

 others. In 1902, Mr. Tokubuchi collected the same fungus on the wild yam in tlie 

 Island Oki in Kiushfi. During my botanical excursion in the Province Ecliigo 

 in the summer of 1908, I had collected the diseased leaves of Dioscorea japonica, 

 and an examination showed that it was also due to the same fungus. Recently, I 

 obtained the same diseased specimen of the cultivated yam from Morioka in Xorth- 

 ern Honshu through the kindness of Prof. G. Ya.mada. These facts show that 

 the disease is very common and very widely distributed throughout our country. 



In the last fall, the present disease severely threatened the yam which was 

 cultivated in the experimental plots of our college and in the adjoining fields. At 

 that time, I had an opportunity of examining the symptoms of this disease as well 

 as the nature of its causal fungus by the fresh materials; and I have been able 

 to recognize that the fungus in question is new to science and the disease itself to 

 have passed unrecorded up to the present time. This short pa])er is intended to 

 report upon some results of my study on this new disease of the yam. 



