Affinities and architecture of Devonian trunks of Prototaxites loganii

Devonian fossil logs of Prototaxites loganii have been considered kelp-like aquatic algae, rolled up carpets of liverworts, enormous saprophytic fungal fruiting bodies or giant lichens. Algae and rolled liverwort models cannot explain the proportions and branching described here of a complete fossil of Prototaxites loganii from the Middle Devonian (386 Ma) Bellvale Sandstone on Schunnemunk Mountain, eastern New York. The "Schunnemunk tree" was 8.83 m long and had six branches, each about 1 m long and 9 cm diam, on the upper 1.2 m of the main axis. The coalified outermost layer of the Schunnemunk trunk and branches have isotopic compositions (δ(13)CPDB) of -25.03 ± 0.13‰ and -26.17 ± 0.69‰, respectively. The outermost part of the trunk has poorly preserved invaginations above cortical nests of coccoid cells embraced by much-branched tubular cells. This histology is unlike algae, liverworts or vascular plants and most like lichen with coccoid chlorophyte phycobionts. Prototaxites has been placed within Basidiomycota but lacks clear dikaryan features. Prototaxites and its extinct order Nematophytales may belong within Mucoromycotina or Glomeromycota.

In vitro degradation of the moss Hylocomium splendens by three pleosporalean fungi

Three darkly pigmented species of conidial fungi of the family Pleosporaceae isolated from plants colonizing the Saskatchewan Glacier forefield were examined for potential roles in the degradation of moss gametophytes. Curvularia inaequalis and Ulocladium atrum isolated from bryophytes Ditrichum flexicaule and Tortella tortuosa , respectively, and Chalastospora gossypii from Saxifraga oppositifolia were inoculated onto autoclaved gametophytes of the moss Hylocomium splendens. All three species of fungi caused mass losses of the moss gametophytes. In vitro enzymatic tests revealed that all three fungi degraded cellulose, while none degraded insoluble polyphenols. When this material was examined by scanning electron microscopy, it was evident that the fungi had eroded the outer wall layer of the moss leaf cells to some extent but not the inner layer containing more lignin-like compounds. Once the outer wall layer was removed, the cells easily disarticulated. It is proposed that accumulations of these phenolics-rich leaf fragments subsequently ameliorate the rooting environment for vascular plants and have the potential to support the growth of basidiomycetes and other fungi, potentially mycorrhizal with pioneer vascular plants.