Article: The disappearing peel technique: an improved method for studying permineralized plant tissues

A new technique is described for the preparation of sections of anatomically preserved plant fossils starting from the simple and well-known cellulose acetate peel method. Improvements of the results obtained by the peel method are described whereby use of very dilute acid allows extraction and observation in planar view of cell walls that are almost always destroyed by traditional methods. The Disappearing Peel Technique has been especially developed for histological investigations of the delicate cell walls of extra-xylary vascular tissue. Fern phloem from a Carboniferous coal ball is used to demonstrate this new method. It includes transfer of the peel to Araldite, dissolving the peel in acetone, complete demineralization of the plant cells remaining on the Araldite and allows optical examination of cell walls under immersion oil. Artefacts in coverslip and peel as well as residual carbonate content of the peel that may simulate cell wall sculpturing are thereby eliminated. Furthermore SEM and TEM observation of the same cell walls previously examined by the light microscope is possible. This technique will be applied to evolutionary studies of vascular tissues in Palaeozoic ferns.