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XXII. 



THE " BROWNIISrG " AND " STEM-BREAK " DISEASE OF CULTI- 

 VATED FLAX [LINUM USITATISSIMUM), CAUSED BY 

 POLYSPOBA LINI n. gen. eb sp. 



By H. a. LAFFERTY, A.R.C.Sc.L, 



Assistant in the Seeds and Plant Disease Division, 



Department of Agriculture and Technical Instruction for Ireland. 



[communicated by DE. GEORGE H. PETHYBRIDGE, B.SC] 



[Plates VIII-X.] 



[Read March 22. Published Au&ust 19, 1921.] 



I. — Introduction. 



During the recent European war a heavy demand for flax fibre from home- 

 grown sources arose, consequent on the cutting off of foreign supplies. Since, 

 owing to the high prices for fibre then prevailing, successful cultivation of flax 

 was highly remunerative to the farmer, it is not surprising that a boom in flax 

 cultivation set in, so that an immediate and large increase in the area under 

 this crop in Ireland resulted. 



This was accompanied in not a few instances by partial or total failure of 

 the crop, which on inquiry and investigation often proved to be due to such 

 causes as unsuitability of soil and unsatisfactory methods of cultivalion and 

 manuring, as well as to the use of inferior seed. 



In a considerable number of cases, however, it appeared evident that 

 specific diseases caused by parasitic organisms were responsible for seiious 

 trouble, and the insufficiency of our knowledge of flax diseases became 

 acutely felt. 



Stimulated by this lack of information, a programme for the scientific 

 investigation of flax diseases was forthwith embarked upon by the Seeds and 

 Plant Disease Division of the Irish Department of Agriculture. 



A general account of the work undertaken and of the results so far 

 obtained has recently appeared in the Department's Journal,^ and a scientific 



' Pethybridge, G. H., and H. A. Lafferby, " Investigations on Flax Diseases," Jour. 

 Dept. Agi-ic. and Tech. Inst. Ireland, xx, 3, 1920, p. o2o. See also xxi, 2, 1921, p. 167. 



