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STUDIES ON THE FLAX RUST. 



BV 



Naouide Mikatsuka. 



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I. Introduction. 



It has been a well-known fact in the flax cultivating regions of Europe, 

 North America and other countries, that a rust disease generally recognized to 

 be caused by Melatnpsora Lint Tul. has seriously damaged its culture. 



The flax rust not only hinders the growth of the plant by attacking its 

 leaves, bracts, pods and stems, but also attacks the fibro-vascular system of the 

 flax-stem and renders it liable to break at the attacked spots. Moreover the 

 black fungus-tissues remain in most cases adhering to the fibers even after the 

 scutching and hackling operations have been carried out. By careful observa- 

 tions, we can trace the black fungus masses (its teleutosori) in the form of very 

 minute fragments attacked to the end of fine strands of hackled fibers. In Japan, 

 the rust disease at present spreads o\er the whole flax regions and its damage 

 is very serious. 



Numerous papers concerning the flax rust disease have been publisheol by 

 many authors in Europe and North i\merica with reference to its causal fungus 

 and preventive methods. Some important points concerning the life-history, the 

 morphology and physiolog)- of the causal fungus however remain to be solved. 



At the suggestion of Profs. K. Mivabe and S. 1x6, the author has taken 

 up the study of the flax rust, since the fall of 1924, and the present paper is 

 merely a preliminary report of his investigations. The writer wishes to express 

 here his sincere thanks to Profs. Mivahic and Pro who have helped him throgh- 

 out the study with useful suggestions and to Assistant Prof. Y. Tociiinai, Miss 



(Transact. Sapporo Nat. Hist. Soc. \, Vt. \, 1928.] 



