Special papers in Palaeontology: 49
<br />Studies in palaeobotany & palynology in honour of Prof W G Chaloner F R S.
<br />M E Collinson and A C Scott (Eds)
<br />187 pp., 27 pls, 42 text-figs.
<br />ABSTRACT. Solitary, discoidal sporangia terminating smooth, isotomously branching systems from the late Silurian (Pridoli) of Long Mountain, Shropshire are identified on morphological grounds as Cooksonia pertoni Lang. Initial examination of untreated spores in coalified sporangia by scanning electron microscopy reveals smooth walls, but no haptotypic features. Transmission electron microscopy indicates that each spore is surrounded by a coalified layer that disappears following exposure to fuming nitric acid, a treatment which also shows layering in the spore wall (exospore) and, in scanning electron and light microscopy, distinct triradiate marks. Such spores can be assigned with some reservations to the dispersed genus Ambi/isporites and allow tentative assignment of this C. pertoni to subspecies pertoni. Comparison with ultrastructural data from extant pteridophyte spores permits discussion on the homology of the layers seen in the fossil, but it remains conjectural whether or not perispore is present, and is partly responsible for the rather featureless appearance of untreated spores.