Indirect immunofluorescence detection of the xylan (LM11) epitope in transverse sections of fern petioles and lycophyte stems. Calcofluor White fluorescence (a, d, g, j, m) shows the full extent of cell walls. (a–c) Autofluorescence of tracheids (t) obscures observation of LM11 binding in Asplenium polyodon. Note also the autofluorescence of the suberin lamellae of the endodermis (e). (d–f) LM11 binding to tracheid cell walls and phloem cell walls of Asplenium loxoscaphoides. (g–i) Abundance of the LM11 epitope in epidermal cell walls and cortical parenchyma of Asplenium rutifolium. Note that the epitope is not detected in the collenchymatous tissue (coll). (j–l) Binding of LM11 to cell walls of scattered cortical parenchyma cells in the lycophyte Huperzia squarrosum. (m–o) In the lycophyte Selaginella grandis, the LM11 epitope is detected in all cortical parenchyma cell walls. Abbreviations: t, tracheids; e, epidermis; phl, phloem; coll, collenchymatous tissue. No primary antibody controls are provided (c, f, i, l, o). Scale bars: 40 μm.