Lecture VII — 101 — Mycothalli and Mycorrhizomes 



tures which appeared like rhizomes with secondary branches, inhabited 

 by an endophyte just beneath the epidermis; and there were finer 

 hyphae internally in the cortex. 



Mycocaryopses and Infection of Aerial Organs: — Since this 

 book is devoted to endophytic roots and infected rooting struc- 

 tures, it is not deemed advisable to enter into a discussion of 

 endophytic infection of other structures. Yet it is established that 

 mycotrophy exists in such plants as Lolium, a grass in which the 

 fungus lives symbiotically with the immature sporophyte. The "seeds" 

 of Lolium, which are strictly fruit and seed together and technically 

 known as "caryopses", harbour a fungus which is said to have been 

 discovered by Vogl in 1897. Described by Guerin, by Hanausek, 

 and by Nestler, in 1898 and by Hiltner in 1899, and by well-nigh 

 a dozen investigators since, the fact of endophytic infection of 

 L. tementulum is well established. Not only does it occur in recent 

 specimens of this grass but Lindau in 1904 described similar infec- 

 tion from grains recovered from an Egyptian tomb about 4,000 years 

 old. But other grasses, according to March al (1902), lack such 

 infection. 



A detailed study of Lolium was made by McLennan (1920), who 

 described intracellular infection in the aleurone layer, hyphae pene- 

 trating also the scutellum wherever the two were in contact. Fungus 

 is present in embryo sac at or immediately after fertilisation, and the 

 ovum is infected before any divisions have taken place in it. Hyphae 

 sometimes extend from base of ovary into staminal filaments where 

 they become peculiarly knotted. In development of the embryo it is 

 seen that endosperm is formed by an "endospermic cambium", and 

 "if the fungus does not keep pace with the absorbing power of the 

 endosperm, no hyphal layer is formed in the ripe grain, but hyphae 

 can then be found in the scutellum and embryo". Endospermic cam- 

 bium persists as the aleurone layer, which receives a supply of nutrient 

 from the fungal system. McLennan concludes that "the association 

 of the fungus with Lolium tementulum and L. perenne is probably a 

 well-marked case of symbiosis, comparable in many respects with that 

 met with in Calluna vulgaris". She also says : L. perenne is unable 

 to fix nitrogen in the total absence of external supplies of combined 

 nitrogen." 



Rayner (1915) had described a constant infection of seed-coats of 

 Calluna but stated that the embryo is never infected, a mycorrhizal 

 infection resulting by infection of the plantlet from the seed-coats. 

 Rayner asserted that the fungus grows through aerial organs of 

 Calluna but Freisleben (1934) decided that infection in this plant 



