Pethybridge and Lafeerty — A Disease of Flax Seedlings. 369 



conidia have been observed, either on the host or in pure cultures, and no 

 evidence has been obtained suggesting a connexion between this species and 

 Gloeosporium or Glomerella. 



VII. — Transmission of the Disease. 



The observations made on diseased seedlings in the early stages of attack, 

 to which allusion has already been made (see p. 361), suggested that the 

 disease might be transmitted by the agency of the seed. 



In order to settle this point, two lots of seed of one hundred each were 

 taken from a sample part of which, when previously sown, had given rise to a 

 certain number of diseased plants. 



These two lots of seed were sown in very carefully sterilized soil contained 

 in sterilized pots, and, after sowing, the pots were kept covered with glass 

 bell-jars in order to eliminate possible contamination of the seedlings from 

 air-borne sources. The seedlings which developed were kept under very close 

 scrutiny, and up to the seventeenth day after sowing no traces of attack were 

 discernible. On the next day, however, five seedlings with the first signs of 

 disease on them were discovered in one of the pots and two in the other. 

 These affected seedlings and others which appeared later were removed from 

 the pots as carefully as possible as soon as they were recognized, this being 

 done each clay up to the twenty-first after sowing. At that time twenty-four 

 had been removed from one of the pots and twelve from the other. 



After the twenty-first day the diseased seedlings, as they appeared, were 

 not removed ; and at the end of the twenty-fifth clay, when the experiment 

 was concluded, ninety-three had been produced in the first pot and eighty- 

 nine in the second. The rapid increase of the disease during the last three 

 days was probably due, to some extent, to secondary infection. Indeed, it is 

 possible that before the twenty-first day some cases of secondary infection 

 may have occurred. For, although the diseased seedlings were removed as 

 carefully as possible, it cannot be maintained that all chance of secondary 

 infection was excluded during the process, especially seeing that the seedlings 

 were in rather close proximity to one another in the pots. 



The result of the experiment shows quite clearly that the disease emanates 

 from the seed ; and further experiments of the same kind both with sterilized 

 and ordinary soil have confirmed this view. 



In the present paper we have purposely confined our attention to the 



attacks of the fungus on seedling flax ; but we may state here that it also 



attacks the leaves and stems of the mature plant. Indeed, acervuli bearing 



abundant conidia have been found on the outer surface of the " seed-bolls " 



(fruit). During rippling and de-seeding it would not be difficult for the seeds, 



3n2 



