360 Scientific Proceedings, Royal Dublin Society. 



and in the following year Johnson 1 -dealt with this disease, calling it '"firing 

 or 'yellowing.'" Johnson's description was not based on any extended study 

 of the disease in Ireland, but was derived mainly from Marchal's 2 account 

 of a disease of young flax plants, which occurs in Flanders, and is known 

 there as vlasbrand or bruhore. 



It is true that the parasite discovered by Marchal was found (in its 

 resting-spore condition at any rate) in the roots of certain flax seedlings sent 

 from the North of Ireland, taken from a crop affected with " yellowing " ; 

 but as to whether this organism is common, or is of serious importance as a 

 cause of " yellowing " in Ireland, we are still largely in the dark. 



Johnson appears to have assumed that " yellowing " and " firing " were 

 one and the same disease, attributable to the same cause. We find, however, 

 that although these popular terms are at times used somewhat loosely by 

 farmers, yet, generally speaking, they are applied to widely differing troubles 

 with the flax crop. 



The term "firing" is usually employed for a disease of flax plants when 

 they are one half or more than one half grown, not when they are only in 

 the seedling stage. Moreover, "firing" is a term applied chiefly to stem- 

 trouble, whereas the most obvious general feature of " yellowing " is the 

 paleness of the foliage, especially in quite young plants. 



Our study of " firing " has not yet progressed far enough to enable us 

 to define it with preciseness, or to state what the cause of it is ; and it 

 is, of course, possible that it may be the -result of more causes than one. 

 Undoubtedly, however, there is a Fusarium disease of flax in this country, 

 which results in damage to the crop,' sometimes spoken of as " firing " ; but 

 all cases of " firing " cannot be explained as the result of Fusarium attack. 



The disease to be dealt with in the present paper has nothing in common 

 with " firing," as usually understood, and it is very different from Marchal's 

 bruhire. 



Although it was first introduced to our notice as a form of " yellowing," 

 and although, under certain circumstances, affected plants do turn more or 

 less yellow, we do not think that the term "yellowing" is really appropriate 

 for the disease, and we do not propose to employ it. Popular terms, such 

 as "yellowing" (flax), "yellow-blight," "curl" (potato), &c, which are 

 applied somewhat indiscriminately to congeries of distinct diseases, should, 

 as far as possible, be avoided. The disease in the present case is often more 

 of the nature of a "damping- off" than of a "yellowing." 



1 Johnson, T. The " Firing " or "Yellowing " of Flax. Journ. Dept. Agrie. and Tech. 

 Inst, for Ireland, vol. i., 1900-01, p. 591. 



2 Marchal, E. Recherches Biologiques sur une Chytridinee Parasite du Lin . Bruxelles 

 1901. 



