Fungus oj Lollum. 275 



by the growiii«r embryo, wiiicli, therefore, ultimately bt.'iiefits by this 

 concentration of hyphae. The cells of the pro-embryo also receive 

 hyphae directly. Plate XXV., Fig. 3, shows a more advanced 

 embryo. Ilie dermatogen has just been cut off, and tlie hyphae are 

 seen to enter right into the substance of the embryo. The endos- 

 perm cells at the extreme micropylar end ar<.' disorganising as a 

 result of the presence of the fungus, and are also included in the 

 figure. 



Stage C . 



I'ext-figure 7 illustrates the external appearance of the ovary 

 when it is approacliing maturity. A considerable amount of 

 endosperm has been formed; the shadowed portion of the diagram 

 indicates the extent and distribution of this tissue. As in the two- 

 previous stages, the ovary is drawn from the ventral surface. 

 The furrow is noticeable at the proximal end, but as yet, is not 

 well developed at the distal extremity. The dorsal proximal end 

 projects beyond the rest of the ovary in the form of a pocket, in 

 which the embryo develops. 



Sections taken at this stage emphasise the facts already disclosed. 

 The great bulk of the nucellus has disappeared, whilst the endo- 

 sperm has increased in a well-marked and definite manner. The 

 hyphae are still abundant, but owing to their absorption by the 

 endosperm they are not as plentiful as in Stage B. The disorgani- 

 sation which takes place all round the periphery of this layer keeps 

 the growth of the hyphae in check, and, consequently, they never 

 over-run the developing grain, but tend to decrease in amount after 

 the first appearance of endosperm. (Plate XXIII.) The food-sui)ply 

 made available to the grass by the digestion of the hyphae is 

 utilised by the young actively growing endosperm cells. This is 

 rendered possible, for the growth in size of this tissue takes place 

 from the outer surface. The outermost layer of the endosperm may 

 be regarded as a cambium, which is active only on its inner sur- 

 face. This meristematic layer divides in the usual manner, and 

 the cells so formed are at first more or less brick-shaped, but gradu- 

 ally assume an approximately spherical form, and attain their 

 adult size. Growth is carried on in this manner until the fruit is 

 practically mature, then this outermost dividing layer ceases its 

 activity, but persists in the grain as the aleurone layer, the 

 cells of which serve as a store of nitrogenous material. This idea 

 of an endosperm ic camhivni is supported by the fact that the nuclei 

 of this layer remain large and intact, even when the cells are- 



