Lafferty — Disease of Cultivated Flax. 265 



The yield of seed from a " browned " crop is a reduced one, and, of course, 

 its quality is inferior. In Ireland, generally speaking, no attempt is made 

 to save flax seed for sowing, and such loss may, perhaps, be regarded as of 

 110 serious consequence. Nevertheless, the work of the Irish Department's 

 Plant Breeding Division in recent years has clearly shown that high- class 

 fibre-flax seed can be produced at home ; and the experience of the late war 

 shows the great risks involved in depending on foreign sources alone for the 

 supply of flax seed. Hence the desirability of endeavouring to find some 

 means of controlling the disease. 



Fcrsistence of the Fungus. — Polyspora lini, sis already stated, has not been 

 found to produce any reproductive bodies other than the thin-walled conidia 

 already described. It has been found, nevertheless, that this fungus can 

 remain alive in a dormant condition in the host tissues for considerable 

 periods, and under seemingly adverse conditions. Thus, flax stems affected 

 with " browning " and containing the fungus wei:e pulled in July, 1920, and 

 allowed to become air-dry in the laboratory. After being subject to these 

 conditions for six months they were exposed to a moist, warm atmosphere in 

 a covered glass dish. In the course of a day or so the fungus recovered its 

 activities. Large numbers of new acervuli were produced on the surfaces of 

 the stems : and the newly formed conidia were found to germinate normally 

 when transferred to films of beef-extract gelatine. 



Affected stems pulled a year earlier than those just mentioned, and kept 

 under similar conditions for eighteen months, showed a very feeble develop- 

 ment of acervuli when placed in a moist, warm atmosphere ; and only a 

 scanty development of conidia took place. Nevertheless, a few of the latter 

 were found to be viable. 



In the ordinary course of events, affected stems after pulling go into the 

 retting pond ; but what happens to the fungus under these circumstances 

 has not yet been fully ascertained. Stems affected with " browning," pulled 

 and retted in 1919, were air-dried immediately afterwards, and were kept in 

 the laboratory in this condition for eighteen months. When placed in a 

 moist, warm atmosphere at the end of this period, further growth of the 

 fungus and development of new conidia could not be detected with certainty. 



No experiments have as yet been carried out with affected steins, either 

 retted or non-retted, exposed to ordinary outdoor weather conditions over 

 the winter. From what has been said above, however, it would appear 

 possible for the fungus to remain alive in affected flax stems over the winter, 

 and for such stems to form starting-points for the infection of the crop in 

 the following season. That the latter is actually the case, however, seems 

 highly improbable. 



In Ireland flax is always grown in rotation with other crops, so that on a 



SOIENT, PROG. E.p.S., VOI... XVI, NO. XXII, 2 N 



