Lecture VII — 97 — Mycothalli and Mycorrhizomes 



An endophytic fungus, thought to be an Ascomycete, is described 

 from prothalli of L. luciduluin and L. obscurum var. dendroideum by 

 Spessard (1922). It enters through rhizoids or through epidermal 

 cells (or, the author suggests that the fungus may be leaving the plant 

 through these structures) and spreads tO' within 2-3 cell layers of 

 meristem. The mycelium is coiled in lower part of prothallus (the 

 fourth layer from outside) and does not enter the palisade. Spore- 

 like bodies were found in L. luciduluin, sometimes with chromatin- 

 like content and sometimes with fine hyphae proceeding from pores 

 as though the body were germinating ; while in some cells were found 

 true spore-bodies. Stokey & Starr (1924) cite fungal infection of 

 L. complanatum, L. obscurum and L. clavatmn; and state that fungal 

 hyphae were usually found in great abundance in the soil in which 

 prothalli were growing. But in culture Barrows (1936) found that 

 an endophyte isolated from a Lycopodium did not aid development of 

 germinating spores of L. complanatum var. flabelliforme; in fact, it 

 proved impossible to grow the plantlets at all beyond a ten-cell stage. 

 In nature. Barrows (1935) found endophytic fungi in gametophytes 

 of Lycopodium sporophytes, including L. annotinum, L. clavatum, 

 L. complanatum var. flabelliforme, L. lucidulum, L. obscurum, and 

 L. tristachyum. 



Mycorrhizomes in Ferns: — Originator of the term "mycor- 

 rhizome" was Dangeard (1891), who described such a structure from 

 several species of Tmesipteris, although not very clearly. He described 

 and figured an apparent Hartig net but said the infection seemed 

 typically endotrophic ; and he figured what appear to be vesicles. But 

 mycorrhizomes have long existed : Andrews describes a fossil mycor- 

 rhizome from a coal-ball; and doubtless there are innumerable fern 

 mycorrhizomes were there eyes to see. A few descriptions of them 

 come from particularly close observers, such as van Tieghem (1870) 

 who found mycelial hyphae of a parasite {sic) coiled about dark 

 masses in large cells of the inner zone of Osmunda regalis and several 

 other ferns. Rayner (1927) cited and figured infection of Pteridium. 

 LoHMAN (1927) showed vesicles in his illustration of Adiantum 

 pedatum and figured an apparent digestion stage for Botrichium. In 

 general, however, ferns remain for future investigation, because 

 they are not, like the pines, an economic group that commands 

 attention. 



Mycorrhizonies in Orchids: — Aside from studies of ferns and 

 fern allies, the only other rhizomes to- be studied for endophytes are 

 those of orchids, except for the following: Kamienski (1881) de- 



