274 



Ethel McLennan : 



Until the endosperm commences to be formed, the fungus has; 

 been increasing in amount at the expense of the nucellus, etc. 

 This increase is only a temporary one, for the liyphae now grow in 

 close contact with the endosperm c-ells. They enter them when 

 the cells are young and not fully formed, and are here seen to be- 

 come disorganised. Tlie food material thus gained by the grass 

 is used in the prejDaration of the reserve store of food, #vhich is 

 later to be deposited in this tissue. Plate XXII., Fig 3, shows a 

 portion of the endosperm and the accompanying hyphae. lliis 

 section was stained with congo red, and the hyphae and proto- 

 plasm stain in tlie same way. Plate XXII. Fig. 4, also shows the 

 close union between the fungus and the grass. This section was 

 stained only with gentian violet, and the hyphae could be traced 

 more readily in the cell itself. Many of the disorganising threads 

 running in the h.ost cells stained blue, and are shown in the figure,, 

 the cells themselves remaining unstained. Plate XXII., Fig. 5, re- 

 peats the structure shown in the two previous figures, but in addi- 

 tion it shows extremely well, lateral branches, which arise from a 

 hyjDha running parallel to the length of the endosperm, and which 

 enter adjacent cells of this tissue, yielding up their food to the 

 embryo grass plant. 



The fungus is most abundant in the region of the ovum, due 

 probably to the fact that the lumen of the embryo-sac begins to fill 

 first around the embryo. In this region the cells are long and' 

 crescent shaped, and have very dense contents. 



The synergidae are still present, and their absorption is no doubt 

 the result of the activity of the fungus, a fact which may help to- 

 explain the pronounced growth of hyphae always present in this 

 position. 



The ovum rs ^ill undivided, although it has increased in size 

 and the cytoplasm has become vacuolar. 



In the intermediate stages between B and C, the division of the 

 ovum and the subsequent growth of the embryo are points of 

 interest. The first division of tlie e^^ is generally transverse, at 

 right angles to the pro-embryo, and each cell usually contains a 

 well-marked vacuole. The fungus ramifying in the nucellus in this 

 part of the sac comes into direct contact with the endosperm, which 

 forms a lining to the pocket in Avhich the embryo grows. The- 

 hyphae are unusually abundant, and are actively transferring food- 

 material from the various parts of the carpel to the endosperm in 

 this area. (Plate XXV., Fig. I.) These cells are later absorbed 



