Pkthybkidgk and Lafferty — A Disease of Flax Seedlings. 375 



The film culture mentioned above was opened, and small portions of 

 the growth (consisting of both mycelium and conidia) were carefully trans- 

 ferred to the cotyledons of four healthy seedlings derived from seeds from a 

 non-infected sample, which, to make assurance doubly sure, had been 

 disinfected with formaldehyde solution previous to sowing. They were sown 

 in sterile sand, and protected from aerial contamination. After fourteen clays 

 all four seedlings were diseased. Four similar seedlings were used as a 

 control, and had drops of sterile water placed on their cotyledons instead of 

 portions of the film culture. They remained perfectly healthy. The experi- 

 ment was repeated, the cotyledons of ten healthy seedlings being inoculated 

 from the growth of the film. The result was as before ; in three clays all ten 

 seedlings had contracted the disease. 



Finally, small portions of the mucilage, taken direct from seeds contain- 

 ing mycelium, were placed on the cotyledons of five healthy seedlings 

 specially grown under aseptic conditions, as in the previous trials. As a 

 control, portions of mucilage from a seed containing no mycelium were 

 placed on the cotyledons of five similar seedlings. In the latter no disease 

 developed ; but all the five seedlings inoculated with the mycelium- contain- 

 ing mucilage became diseased within a fortnight. This experiment was also 

 repeated, ten further healthy seedlings being inoculated as before. In four 

 days all of them had become diseased. 



Summarizing all these results, it is clear that the mycelium present in 

 the epidermis of infected seeds is, in the majority of cases, living, retains its 

 infective power, and is that of Colletotrichum linicolum. The infection of the 

 crop undoubtedly occurs by means of this hibernating mycelium present in 

 the epidermis of the seeds. 



The precise method by which the seedlings become infected from the 

 seed has not yet been determined ; but no evidence could be found to 

 support the view that the fungus reached the embryo by passing through the 

 seed-coat. It may possibly be the case that during germination or after- 

 wards the mycelium grows from the mucilaginous epidermis of the seed, and 

 passes directly into the seedling, causing infection wherever the mucilage 

 may happen to come in contact with it. "When the seed-coats are carried 

 above ground, this is most frequently on one or both cotyledons. 



We are inclined to think, however, that infection is probably indirect, 

 and that it takes place from conidia, which are produced by the hibernating 

 mycelium, and which subsequently come into contact with some part of the 

 seedling, where the production of germ tubes would take place, and penetra- 

 tion would occur. The production of such conidia has been observed on the 

 surface of infected seed-coats, when carried above ground by the cotyledons, 



SCIENT. PEOC. K.D.S., VOL. XV., NO. XXX. 3 



