264 Scientific Proceedings, Royal Dublin Society. 



stem lesions in the region of the soil-level which cause the plant to "damp off." 

 In cases of attack by P. lini the affected spots on the cotyledons are darker in 

 colour, and do not increase in area rapidly, so that the cotyledons remain 

 alive for a considerable time after infection has taken place. True, as 

 mentioned in au earlier part of this paper, lesions due to P. lini have been 

 found on the stems of affected plants in the region of tlie first node, as a 

 result of which the latter fall over; but this condition of things generally 

 occurs at a later stage, when the flax is at least six inches high, and it in 

 no way resembles "damping off," as found in "seedling blight." 



When there is any doubt as to which organism is at work the matter can 

 easily be settled by microscopical examination of the acervuli present on the 

 diseased areas. If P. liniis responsible, these acervuli will agree with those 

 herein described ; but if C. linicohcm is the active parasite, the acervuli will 

 be found to be made up of conidia borne singly in succession on conidiophores, 

 while from the bases of the acervuli long, black, tapering setae arise. 



As the seedlings affected with P. lini grew in size, some of the new 

 lea,ves produced became infected through various agencies, from conidia 

 present on the diseased cotyledons. From these leaves, in turn, adjoining 

 plants became infected, with the result that when the crop was half grown 

 the disease was general, though not very obvious. Some plants exhibited 

 the "stem-break" form of injury, and were either dead or dying, while the 

 leaves of others were spotted, and in a few cases minute elongated brown 

 marks were making their appearance on the stems. 



This state of affairs persisted until after the plants had flowered and the 

 fruits were beginning to be formed. Then the fungus became more virulent, 

 possibly owing to the decreased vitality of the plants or to some change in 

 the environmental conditions, and " browning " of the leaves, stems, branches, 

 and fruits became most pronounced. Thus it is seen that the fungus which 

 causes " browning " is present, though not to a large extent, on some of the 

 flax plants, at least from a very early stage in their development. 



VII. — Control of the Disease. 



The losses due to " browning " and " stem-break " are, in many cases, 

 very serious, although naturally it is a difficult matter to estimate them 

 quantitatively with accuracy. 



"Browned" stems tend to break in the regions of the diseased areas 

 during scutching. Thus the fibre is shortened, and much of it escapes with 

 the tow. Further, plants affected with " stem-break " may be dead and 

 useless at pulling time, and, in any case, are most likely to be left behind 

 when the crop is pulled. 



