Pinna anatomy of Syagrus harenae using LM with cross-sections. A. Bisseriate hypodermis (hy) between the adaxial non-vascular fibre bundles (fi). Adaxial epidermis (ad), cuticle (cu). B. Arciform subsidiary cells (two red dots) and guard cells (two black dots) are at the same level as the abaxial epidermis (ab). Cuticle (cu), hypodermis (hy), substomatal chamber (sc). C–D. Minor fibres (three white circles) and rounded groups with many fibres (three black circles). E. Primary (t1) vascular bundles connected to the adaxial hypodermis, secondary (t2) vascular bundles unconnected, and tertiary (t3) vascular bundles connected only to the abaxial hypodermis. F. Secondary (t2) vascular bundle abaxially surrounded by a sclerenchymatous sheath (ss). G. Tertiary (t3) vascular bundle abaxially surrounded by a sclerenchymatous sheath (ss). H. Primary vascular bundle: protoxylem (pr), metaxylem (me), two poles of phloem (ph) and sclerenchymatous sheath (ss) connected to hypodermis on both surfaces. I. Pinnae margin: large first (lf) adaxial non-vascular fibre bundles and adaxial tertiary vascular (t3) bundle. J. Midrib: fibrous (fr) ring reaching the abaxial hypodermis (black arrowhead) and interrupted expansion tissue (et). K. Detail of the expansion tissue: fibres (fi). L. Collateral fibre bundles (five black circles) and phloem poles (ph). M. Non-vascular (nv) fibre bundle. N. Accessory bundle (ab). Photographs by Bruno F. Sant’Anna-Santos.