438 FOSSIL PLANTS/Fungi and Lichens Figure (A) Fungal spore from the Early Devonian Rhynie Chert, with its outer surface densely covered by parasitic chytridiomy cetes (arrows); scale bar: 50 mm (From Taylor TN, Remy W, and Hass H (1992) Fungi from the Lower Devonian Rhynie Chert: Chytridiomycetes American Journal of Botany 79: 1233 1241.) (B) Parasitic chytridiomycete (arrow) that has developed between the wall layers of a fungal spore from the Rhynie Chert; scale bar: 10 mm (C) Longitudinal section through a perithecium of a Rhynie Chert ascomycete; scale bar: 100 mm (D) Detail of Figure 1C, showing part of the perithecium with several asci containing ascospores; scale bar: 15 mm (E, F) Vesicular arbuscular mycorrhiza in the Rhynie Chert land plant Aglaophyton major ; (E and F adapted from Taylor TN, Remy W, Hass H, and Kerp H (1995) Fossil arbuscular mycorrhizae from the Early Devonian American Journal of Botany 87: 560 573.) (E) hyphae with vesicles of the mycorrhiza fungus Glomites sp.; scale bar: 100 mm; and (F) Glomites arbuscule within a cortical cell from an aerial axis of A major ; scale bar: 10 mm (G) Section of the thallus of the Rhynie Chert lichen Winfrenatia, showing depressions that contain cyanobacteria (arrows) surrounded by more a opaque zone that represents the mycobiont; scale bar: 50 mm (H) Detail of Figure 1G, showing part of a single depression containing unicellular cyanobacteria and fungal hyphae that form a net like structure; scale bar: 25 mm sacs (asci) that contain unicellular to up to five times septate sexual spores (ascospores) (Figure 1D) Plants with abundant woody tissues first appear in the Middle to Late Devonian, and it is at this time that the first wood-decomposing fungi – basidiomycetes – appear The earliest fossil evidence for the possible existence of basidiomycetes occurs in the form of branching hyphae of varying diameters