LAFFER'r\- — Disease of Cultivated Flax. 249 



paper dealing with one new specific disease, " Seedling Blight," has also been 

 published.! 



The present paper deals with another previously unrecognized disease of 

 flax which has been proved to be caused by a fungus hitherto undescribed, 

 and in which a general " browning " of the crop, accompanied by the fracture 

 of many of the stems of the plants, are characteristic features. Up to the 

 present this disease has not been described as occurring in any other country. 

 Nevertheless, there is reason for believing that it must occur elsewhere ; and 

 it seems not improbable, from a preliminary note on a disease of flax in 

 Holland, provisionally ascribed to a species of Gloeosporium, published in 

 1914, that the case in question was one of " browning."- The disease occurs 

 in Ireland on flax grown from Dutch seed rather more frequently than on 

 crops grown from seed from other countries. The fungus causing it has 

 been found on seed derived from crops grown in England and Scotland and 

 on seed believed to have been raised in Belgium. The disease has appeared 

 in Ireland on crops from seed purporting to have been raised in England, 

 Scotland, Holland, Eussia, Canada, and Japan, and it is believed to be present 

 in British East Africa. 



II. — Symptoms of thk Disease. 



As stated above, the disease manifests itself in two principal forms, and 

 for these the popular terms " browning " and " stem-break" are suggested as 

 suitable. 



1. General features — {a) " Broioning."^ — To the casual observer "browning " 

 first becomes evident about pulling time. The actual time depends to a 

 large extent upon the earliness or lateness of the particular season, but in 

 normal years it is usually towards the end of July or the beginning of August. 

 At this time isolated areas in the crop, of various shapes and sizes' take on a 

 distinct brown colour, so that they contrast somewhat strongly with the still 

 green surrounding plants. Gradually these patches increase in extent until 

 they coalesce, and the entire field becomes more or less uniformly brown. 

 Occasionally, when primary infection is more general from the start, 

 " browning " develops in a more or less uniform fashion over the whole ci'op, 

 instead of appearing first in isolated areas. 



' Pethybridge, G. H., and H. A. Laflferty, " A Disease of Flax Seedlings caused by a 

 Species of Colletotrichura and transmitted by infected seed," Sci. Proc. Roy. Dub. Soc, 

 XV. (N. S.), 30, 1918, p. 359. 



2 Meded. v. d. Rijks Hoogere Land-, Tuin- en Boschbouwschool, Wageningen, vii, 

 1914, p. 53. 



3 " Browning " is sometimes, but erroneously, referred to as "firing." True " firing " 

 is a very dififerent disease, and is caused by Melampsora lini, one of the rust fungi. 



SCIENT. PBGC. E.D.S., VOL. XVI, NO. XXII. 2 M 



