372 Scientific Proceedings, Royal Dublin Society. 



emerged, were subjected to minute scrutiny. On one cotyledon of each of 

 four seedlings small, reddish spots were observed at a very early period 

 These spots, however, did not increase in size, and no fungus appeared 

 on any of them. Eventually the cotyledons were sectioned and examined 

 microscopically. It was found that the redness was due to the presence 

 of anthocyan in certain of the cells, but they were apparently quite healthy, 

 and no fungus hyphae were associated with them. 



On the ninth day a small water-soaked area was observed on one of the 

 cotyledons of a fifth seedling which up to that time had shown no sign what- 

 ever of discolouration or of fungus attack of any kind. Microscopic examination 

 showed that this was a case of Colletotrichum attack. This was the only 

 seedling out of the twenty-eight which showed any disease. The evidence in 

 this case pointed clearly to the fact that the cotyledon was not already 

 affected whilst within the seed, and infection must have been subsequent to 

 germination. In spite of careful search we have in no single instance obtained 

 the slightest evidence in favour of the view that the embryo is already 

 infected while still within the seed ; and we are of opinion that seedling 

 infection is from an external source, and occurs during the course of, or 

 subsequent to, germination. 



The next step taken was to examine one by one the individual seeds in a 

 naturally infected sample. This was done by placing each seed in a drop of 

 water on a microscope slide and allowing the seed to swell. The mucilaginous 

 epidermis of the seed-coat was then examined carefully. Nothing was found 

 in the first few seeds examined, but it was soon discovered that in some of the 

 seeds fungus mycelium in considerable amount was present in the cells of the 

 epidermis. (See fig. 4, Plate XIX., and fig. 7, Plate XX.) 



This mycelium was very similar in all the cases in which it was found. 

 It was septate and hyaline ; and in one case appressoria were found, similar 

 to those already described (see p. 364), which at once strongly suggested 

 that it might be that of Colletotrichum. Some of the cells of the hyphae 

 were empty, but many of them retained their protoplasmic contents and 

 presented every appearance of being still alive. 



After a little practice it was found comparatively easy to pick out with 

 the naked eye seeds containing mycelium. Such seeds have a dull appearance, 

 and are often somewhat dark in colour and slightly roughish on the surface 

 owing to the partial absence of the cuticle. Probably this last-named feature 

 explains why such seeds were found to swell up, when placed in water, more 

 rapidly than the normal-looking seeds, the absence of cuticle facilitating the 

 rapid imbibition of water by the remainder of the cell wall. 



The amount of mycelium present varied considerably from seed to seed, 



