Kelley — 52 — Mycotrophy 



Summary: — There are no records of mycorrhizae in fossil Angio- 

 sperms because, so far as we are aware, there are no descriptions of 

 fossil angiospermous root structures. Impressions of aerial organs in 

 clay beds give us no clue to the subterranean organs ; but since mycor- 

 rhizae were so well developed in the lower plants, it would perhaps 

 not be an unwarranted assumption that they occurred in higher plants 

 also. The general picture of ancient life that the fossil record gives 

 us is a duplicate of the one we see today : There were forests and on 

 the forest floor was leaf litter and mould in which saprophytic fungi 

 lived ; and the rootlets and other subterranean structures of ferns, 

 lycopods and trees were invaded by fungal hyphae as they are today, 

 and these hyphae produced swellings and vesicles that give the pre- 

 pared sections a modern appearance. Then, too, there are "digestion 

 stages" that indicate phagocytosis occurred in those old mycorrhizae. 

 Mycotrophism is by no means a new process, for it appears coinciden- 

 tally with the appearance of rooted plants. The explanation of myco- 

 trophism on any developmental basis involves serious problems. 



"The antiquity of fungi also raises again the question of their 

 origin, whether they came from the Algae or from one or more 

 separate and distinct phylogenetic lines. The sum of geological 

 evidence appears to favor the conclusion that they have been distinct 

 from the beginning and should not be placed in the same phylum 

 with the algae." Wolf and Wolf, The Fungi, vol. 2, p. 488, 1947. 



