278 Etltel McLennan : 



the space formerly occupied by tlie nucellus, the outer parts of 

 which are the last to disappear. Starch cells continue to be formed 

 until the seed is almost ripe, and the hyphae nourish these young- 

 starch cells, just as they did the inner, now mature, starch cells, in 

 the younger stages already described. 



When the endosperm attains its full size, the outer dividing 

 layer ceases to function, and becomes the young aleurone layer. 

 The cells, which constitute it, retain their embryonic form, as. 

 regards both their size and shape, in their adult condition. They 

 eventually thicken their walls considerably, and their contents be- 

 come packed with aleurone grains, so that finally the nitrogenous 

 layer characteristic of the endosperm of cereals is formed. 



Plate XXIV. illustrates a section of the endosperm taken at the 

 stigmatic end of a grain, at a stage Avhen the aleurone layer is not 

 yet adult. The hyphae, which by this time are in the form of a 

 layer, take jjart in the nourisliment of the aleurone cells. Just, as 

 in the case of the starch cells, they actually enter into the cell cavity 

 by penetrating the cell-wall, and become absorbed by the protoplasm 

 which converts the nourishment so obtained into the aleurone grains^ 

 which are present in great abundance in the adult layer. Ihis 

 plate shows several hyphae passing through the walls and disap- 

 pearing into the cell-contents. 



The aleurone cells figured are young. They show a well-marked 

 nucleus, and are filled with protoplasm, in the mes.hes of which 

 aleurone grains are being formed. The absorption of the hyphae 

 continues until the cells are packed with grains, and the seed is 

 nearly ready for ripening. A section of a fully mature noi-mal 

 endosperm shoAvs, however, no signs of the endophytic nature of the- 

 fungus. 



It is interesting to note that Peklo (16) suggested that the 

 aleurone layer was probably fungal in origin in all cereals. The 

 suggestion arose as a result of an incidental examination of some 

 Loliian temulentiim grains. In order to carry tue investigation 

 further he decided to examine grains of Triticum, Secale, and 

 Hordeum. He recognised the necessity of examining rust-resistant 

 types, and stated fully in his paper tlie varieties he proposed to- 

 examine. AVith the forms chosen he obtained negative results. Not 

 deterred, he next examined material he already had embedded in 

 paralhn, but he did not state its origin, or given any information; 

 regarding its rust-resistant capacities. 



