Indirect immunofluorescence detection of mannan (LM21) epitopes in transverse sections of fern petioles and lycophyte stems. Calcofluor White fluorescence (a, f, j, n, r) and bright-field (b) showing the full extent of cell walls. (a–i) Localisation of the LM21 epitope in and around the vascular bundle of Asplenium elliottii. The epitope is detected in the cell walls of tracheids (t) and sclereids (scl) that surround the vascular bundle. A high magnification shows detection of the LM21 epitope in the inner cell wall layer of sclereids (f–i). Note red autofluorescence of sclereid cell walls (d, h). (j–m) LM21 binding to the innermost cell wall layer of sclerenchyma hypodermal cells (hyp) and the sclereids of an Asplenium elliottii petiole. Note red autofluorescence of sclereid cell walls (l). (n–q) Immunodetection of LM21 in sclerified epidermal cell walls and subepidermal tissue of Hymenasplenium obscurum. Note red autofluorescence of sclerified epidermis and subepidermal tissue (p). (r–u) Unmasking of the LM21 epitope in primary cell walls of the cortical parenchyma of Todea sp. after pectate lyase treatment (PL). Note that cell walls of the vascular bundle and surrounding sclereids (scl) are labeled prior to pectate lyase treatment. (v, w) Detection of the LM21 epitope in the collenchymatous strengthening tissue of Equisetum ramossisimum. (x, y) Strong binding of LM21 to tracheids and weak binding to cortical parenchyma in the lycophyte Huperzia squarrosum. Abbreviations: scl: sclerenchyma; phl: phloem; ep: epidermis. Abbreviations: t, tracheids; scl, sclereids; scler, sclerified tissue; e, epidermis; par, parenchyma, coll, collenchymatous tissue. No primary antibody controls are provided (e, i, m, q, u, w, y). Scale bars: 40 μm.