260 Scientific Proceedings, Royal Duhlin Society. 



The rate of development of " browning " is intimately connected with the 

 weather conditions prevailing at the time, being more rapid in damp warm 

 weather than under relatively dry atmospheric conditions. One diseased centre, 

 approximately one square foot in area, kept under observation, was found to 

 have increased in three days to an irregular area of about seventy-two square 

 feet. Some farmers have long recognized the epidemic nature of the trouble, 

 and they endeavour to pull the crop as soon as " browning " makes its 

 appearance 



When individual plants collected from a "browned" patch are carefully 

 examined, it is seen that the fruits, sepals, leaves, and stems show brown 

 diseased areas on their surfaces ; and it is to the effect of these when seen in 

 mass that the general browning of the crop is attributable. 



On the still partially green leaves the diseased spots, which are generally 

 rounded in outline, may occur either singly or in considerable numbers, as many 

 as eight having been counted on a single leaf. They are dark brown in colour, 

 and, as a rule, sharply marked oif from the surrounding tissues, while they 

 are slightly depressed below the level of the normal leaf-surface. As the 

 spots do not increase in size very rapidly, the affected leaves remain only 

 partially attacked, and are able to continue their functions to a considerable 

 extent for some time after infection. In those cases, however, where a leaf 

 becomes attacked in the region of its petiole, death of the whole leaf quickly 

 ensues. In all cases, irrespective of the region of attack, an affected leaf 

 dies prematurely, turns brown, and either falls off the plant or remains with 

 its surface adhering to the stem. 



On the main stem the diseased areas are often closely associated with the 

 pi'esence of a diseased leaf situated at a slightly higher level. They are first 

 apparent as minute elongated spots, which are light fawn to brown in colour. 

 Gradually the spots increase in size, especially in a longitudinal direction, and 

 they may even coalesce, laterally as well as longitudinally, until practically 

 the entire surface of the stem is involved (Plate A'^III, fig. 2). 



In dry weather the cortex often ruptures lengthways along a diseased 

 area, and the stem, when bent at right angles at such a place, has a strong 

 tendency to break ; such a brittle condition is, of course, quite foreign to 

 healthy flax. 



The attack on the branches is similar to that on the main stem ; but, 

 owing to the smaller diameters of the former, the diseased areas more 

 frequently encircle them completely. 



Diseased sepals turn brown, and generally adhere firmly to the wall of 

 the fruit. 



Affected fruits are easily identified in the earlier stages of attack while 



