280 Ethel McLennan: 



am led to the conclusion that it is a result of the part played hj 

 the fungus during the development of its host. The grass so con- 

 trols and subjugates the mycelium during the changes which take- 

 place after fertilisation, that the embryo-sac, as its increases in size, 

 pushes the fungus closer and closer to the periphery, until the 

 mature condition is reached. Not only is the hyphal layer found 

 between the endosperm and the testa, but, if the fungus is active, 

 remnants, may be found all round the periphery of the embryonic 

 area, in fact, in any position occupied by them during the later 

 embryological stages. (Plate XVIII. Figs. 1-5.) 



The embryo during this period follows the usual course of 

 development. At Stage C it was an undifferentiated club-shaped 

 body, and hyphae were in close association with its micropylar 

 end. 



The next marked period of growth results in the appearance of 

 the stem apex (Plate XXV., Fig. 4.) This is followed by differen- 

 tiation of the radicle and elongation of the cotyledon. When all 

 the parts of the embryo are thus marked off from one another, 

 growth continues until the embryo is fully developed. The fungus,, 

 in the meantime, can generally be seen at both the micropylar end, 

 and also, between the developing scutellum and endosperm. It is 

 generally pronounced in the region of the plerome cells of the 

 cotyledon. 



Further investigations of the development of the embryo have 

 been commenced in order to determine more exactly the relation of 

 the fungus to its later development, as it is possible that the 

 fungus plays a jole in the formation of the scutellum comparable to 

 the one it plays in the formation of the endosperm. 



The hyphae, already in the very young embryo, follow the 

 development of the stem-apex, and remain localised in their growth 

 until germination takes place. 



The Fungus hi the riant. 



The growtli of the fungus keeps pace with that of the plant, the 

 hyphae, however, are mainly restricted to the growing apex, but 

 can be seen extending for a short distance down the stem. Ihey 

 show the dual staining property already described (pg. 



Even at this stage the intra-cellular nature of the fungus can 

 be demonstrated. vSome of the parenchymatous cells of the grass- 

 are invaded, and used as a food supply by the hyphae. Sucli cells 

 always stain with gentian violet, and they show a dense network of 



