270 Etltel McLennan : 



While these changes ane proceeding in the carpel wall, tlie hyphae 

 in the developing ovule are not quiescent. Ihey keep pace with the 

 .growth of the ovuLe, and until the embryo-sac is at the 8-celled stage 

 they simply run between the cells of the nucellus, ramifying in 

 every direction. They extend right through the nucellar tissue 

 •completely surrounding the embryo-sac. Freeman, when discuss- 

 ing the ovary of Lol'nim temideufuni at this stage, states that hyphae 

 are completely wanting on the outer dorsal surface towards the 

 embryo-sac end, stopping at about the level of the antipodal group. 

 If this i8 so, it is difficult to see how hyphae come to be present in 

 this position in the mature grain. As far as I have observed they 

 are uniformly distributed through tlie inner layers of the nucellus, 

 ])ut do not gienerally extend into the very outer layers until later 

 in development. The dual staining properties are shown by these 

 hyphae, but the great majority of them will pick up thie purple 

 istain. 



The first indication of any change in the relation between the 

 fungus and the cells of the ovule at this stage is the tendency for 

 tlie hypliae to form knots (Plate XXI. Fig. 3). These are especially 

 striking if tlije sections are cut rather thicker than those to be used 

 for detailed high power examination. Hanausek described the 

 occurrence of knots (Knauel) in the ovary of Darnel, and figured 

 them. I have been unable to obtain his original paper, only 

 abstracts witliout figures being available. He offered the occur- 

 rence of these knots as evidence in favour of the fungus being 

 related to the Ustilac/ineae. Freeman says : ''I have found no 

 such knotting of hyphae to indicate the commencement of Ustilagine 

 spore formation." These knots undoubtedly do occur, but are 

 rather to be regarded as the first stages in the penetration of the 

 nucellus cells. The hyphae arch round all sides of the cell before 

 entering it, and as they generally invade two or three adjacent 

 ■cells simultaneously, this arching gives the knot-like formations 

 above described. I do. not think they afford any clue to the actual 

 systematic position of the fungus in question. Since they are just 

 on tlie point of attacking a cell t]j"y are rich in ferments and 

 •always stain vividly. 



Cells showing a later stage of invasion are also present in such 



an ovule. Lateral branches arise from these enfolding hyphae, 



which penetrate tlie cell wall and pass into the substance of 



the cell itself. It soon becomes filled wath a dense network of 



^threads, and in this condition forms a most striking part of the 



