FOSSIL ECTOMYCORRHIZAE FROM THE MIDDLE EOCENE

Fossil ectomycorrhizae were found recently among permineralized plant remains in the middle Eocene Princeton chert of British Columbia. The ectomycorrhizae are associated with roots of Pinus and have a Hartig n et that extends to the endodermis, a pseudoparenchymatous mantle, and contiguous extramatrical hyphae that are simple-septate. The mycorrhiz al rootlets lack root hairs and dichotomize repeatedly to form large, coralloid clusters. Reproductive structures are absent. Based on the m orphological characteristics, and the identity of the host, the closel y related basidiomycete genera Rhizopogon and Suillus are suggested as comparable extant mycorrhizal fungi. These exquisitely preserved spec imens represent the first unequivocal occurrence of fossil ectomycorrh izae and demonstrate that such associations were well-established at l east 50 million years ago.