A reexamination of fungi within the roots of the fossil conifer, Metasequolia milleri Rothwell and Basinger reveals well-developed Paris-type vesicular-arbuscular mycorrhizal (VAM) associations. Metasequoia milleri has been reconstructed from permineralized specimens that occur within the extensive wetland biota of the middle Eocene Princeton chert from southern British Columbia, Canada. Roots of M. milleri are diarch with compact wood, a prominent endodermis, parenchymatous cortex and a uniseriate epidermis. The smallest roots lack secondary tissues, and show extensive growth of mycorrhizal fungi comparable to that seen in squashes we have made of living M. glyptostroboides Hu & Cheng roots. Both the living and fossil roots are characterized by cortical cells containing intracellular hyphal coils that branch to produce arbuscules. Intracellular coils are much more common in the living species than in the fossils, but abundant arbuscules develop from coils throughout the cortical regions of both. Paris-type VAM associations occur among living terrestrial embryophytes ranging from bryophytes to flowering plants. Among living conifers, Paris-type VAM associations are widespread in the Podocarpaceae, Taxodiaceae and Taxaceae. The remarkable similarity of the fossil and living mycorrhizae of Metasequoia demonstrates that an essentially modern symbiotic relationship has existed in this genus for at least 50 million years, and further strengthens hypotheses about the antiquity of mycorrhizal associations among land plants.

Key words: Eocene, Metasequoia, mycorrhizae