258 Ethel McLennan : 



does not seem to be a feasible one. Of course it niiglit be argued 

 that the two grasses contain different species of fungi, one of which, 

 might be toxic, the other liarmless. Ihe actual identity of the 

 fungi obtained ,from the grains can only be established when they 

 are grown artihcially, and the sporing stage obtained, but as far 

 as one can judge by comparing the two forms, they are very simi- 

 lar, and are certainly very closely related if not actually identical. 

 Seemingly the explanation of the cause of the poisonous nature 'if 

 Darnel must be looked for elsewhere, and is not to be furthered by 

 a study of the fungus found inhabiting it. 



Freeman, when discussing the fungus in the embryo of the grain, 

 records some experiments which were undertaken in order to inves- 

 tigate the function of the nucellar layer of hyphae, although it is 

 not quite clear what bearing they have on this point. He grafted 

 embryos of Loliinn ttiiuihiitiim on endosperms of Lolivm 'perenne, 

 and vice versa, the grains having previously been sterilised, and 

 all manipulations carried out under sterile conditions. Thirty- 

 four grafts of Loliinn perenne embryos on IJ>Jliiin teniulentitm 

 endosperms were made, and of this number eighteen germinated. 

 He examined two of these seedlings, and found both contained 

 hypliae, from this lie argued it was very probable that " liypliae 

 from the infection layer of the />. terniilentmn grains were able to 

 gain entrance to the embryos of Loliiim perenne/'' These experi- 

 ments really lead nowhere, for the hyphae are already in the rye 

 grass end)ryos before grafting on any foreign endosperm, and their 

 jjresence cannot possibly be due to infection from the nucellar 

 hyphal layer or from his loialised infection area. 



Disfrihiition of tJie fi/nr/iis in the f/rain^ 



Many grains of Loliinn jterenne were sectioned with a view to 

 determining the distribution of the fungus in the fruit. Transverse 

 sections taken at different levels are shown in Plate XVIII., Figs. 

 1-3. The yellow line illustrates the distribution of the fungus. A 

 transverse section at the distal end of the grain, Fig. 1, shows the 

 hyphal distribution to be co-extensive with the aleurone layer. A 



4. Following upon Brown and Morris (11), I have adopted the follow- 

 ing terminologj- in describing the grain. The furrowed side of the grain is 

 the ventra} STirface, the side opposite to this the dorsal. The embryonic 

 end is called proximal, while the stigmatic end, or that portion remote from 

 the embryo, is distal. A section passing through the ventral and dorsal sur- 

 face is a sagittal section, while the longitudinal section at right angles to 

 this is a coronal section. The sagittal plane which divides the grain into 

 two equal halves is the median sagittal plane. A section at right angles to 

 both sagittal and coronal planes is tra^isveisc. 



