Lecture IV — 49 — Fossil Mycorrhizae 



Then, again, it must be realized that few students of fossils have any 

 keen interest in mycorrhizae, and many examples of our science may 

 languish in slide-boxes as in sarcophagi of our science. When it is 

 realized that morphologists looked at the Hartig net in roots of woody 

 plants for many years before realizing that they dealt with anything 

 more than "curious thickening strips", and even today are inclined to 

 ignore or at best to tolerate mycorrhizae, it is not to be wondered that 

 palaeobotanists, who have even less interest, should have succeeded 

 so well in ignoring them. 



Fossil Ferns and their Endophytes: — There are three papers 

 dealing with fossil mycorrhizal ferns. The first paper, by Seward 

 (1924), deals with the fern Tempskya from Montana. "Some roots 

 have lost the x)'lem, and the centre is occupied by a group of dark 

 brown bodies that may be coprolites of a small insect or, in some 

 cases, possibly escaped cell contents. Entomologists whom I have 

 consulted have not been able to identify the oval bodies with the 

 activities of any known boring animal : no trace of any insect has 

 been discovered. Attention has elsewhere been called to the resem- 

 blance of these bodies to the supposed coprolites frequently found in 

 tissues of Carboniferous plants." Seward figures the same sort of 

 bodies as those figured by Janse (1897) for Celtis, and the writer 

 found similar structures in Juglans collected at Mont Alto, Pennsyl- 

 vania. 



In Osmundites Dozvkeri, "The ground tissue cells contain traces 

 of distinct fungal hyphae, and in many of the parenchymatous ele- 

 ments the cavity is completely filled with spherical vesicles ; in other 

 cases one finds hyphae in the center of the cell while vesicles line 

 the walls. Carruthers refers to these bladders as starch grains, and 

 this may be their true nature ; their appearance and abundant oc- 

 currence in the parenchyma certainly suggest vesicular cell-contents 

 rather than fungal cells. I could detect no proof of any connection 

 between the hyphae and bladders, and the absence of the latter in 

 the cavities of the tracheids, favoured the view of their being either 

 starch grains or other vacuolated contents similar to that in the cells 

 of the Portland cycad referred to." (Seward, 1898). 



The third paper on fossil ferns is by Andrews and Lenz (1943), 

 who describe a petrified Coenopterid fern stem from the Middle 

 Pennsylvanian of Illinois, which contains an abundant mycelium in 

 the cortex. The fern stem, or possibly a rhizome, has been described 

 by Andrews as Scleroptcris illinoiensis, and the mycelium is found 

 within host cells throughout the cortex although it is somewhat more 

 abundant in the middle and inner regions. Hyphae were also found 



