374 Scientific Proceedings, Royal Dublin Society. 



one showed a slight development of Altemaria and the other no fungus 

 growth. It is clear that in one case, at least, the mycelium originally present 

 in the epidermis was dead. The experiment shows that although the mycelium 

 of the epidermis of the infected flax seeds may not in every instance be alive, 

 yet it is so in the majority of cases. 



In another experiment twenty seeds, each found by microscopical 

 examination to have mycelium in its epidermis, and twenty others, in 

 which mycelium could not be found, were sown in moist, sterilized silver 

 sand. The twenty non-infected seeds produced the same number of seed- 

 lings, of which fifteen bore their seed-coats aloft. Examination of the 

 mucilage of these seed- coats (which was done by carefully removing a little 

 of it without removing the seed-coats themselves) showed no trace of any 

 fungus ; and all of the seedlings remained free from disease up to the end of 

 the experiment. From the infected seed eighteen seedlings were produced, 

 thirteen of which carried their seed-coats on the cotyledons. In each of the 

 thirteen cases Colletotrichum, bearing conidia, was found on the seed-coats, 

 which were left in situ. All of these thirteen seedlings subsequently became 

 infected with the disease, as also did four others of those derived from the 

 infected seed which did not carry up their seed-coats. At the conclusion of 

 the experiment, which lasted a fortnight, the seventeen infected seedlings 

 were all dead. One, free from the disease, remained alive. This plant may 

 have escaped infection by chance, or the mycelium in its seed-coat may have 

 been dead from the start. 



These two experiments practically prove that not only is the mycelium 

 in the epidermis of the infected seed in most cases alive, but also that it is 

 that of the Colletotrichum which causes the disease. 



Further proof of these two important points was obtained from the 

 following experiments : —Seeds containing the mycelium were soaked in 

 sterile water until they became mucilaginous. A small portion of the mucilage 

 was carefully removed to an oat-extract-agar film on the lower surface of a 

 cover- glass, which was then placed over a cavity on a microscope slide, and 

 subsequently vaselined around its edges. The preparation was examined at 

 frequent intervals, and on the second day it was found that the hyphae in 

 the mucilage had begun to grow. Growth continued and increased for some 

 days, and on the ninth day the characteristic dark cells (appressoria) and 

 conidia of Colletotrichum were produced. 



This result was confirmed by another experiment, in which small portions 

 of the mucilage, containing mycelium, were placed on slants of oat-extract- 

 agar in test-tubes. Growth in this case was more rapid than on the film ; 

 and Colletotrichum conidia were produced within seven days. 



