Midrib anatomy of Syagrus montana (A–E) and S. evansiana (F–J) using LM in transverse sections. A. Triangular midrib: collateral bundle (white circle), continuous expansion tissue (ex) with linearly arranged fibres (two yellow circles), accessory vascular bundle (white arrowhead), and non-vascular fibres (four black arrowheads). B–C. Detail of the expansion tissue: only non-vascular fibre bundles (black circle). D. Biseriate hypodermis (hy) with thickened walls. E. Detail of the collateral bundle: phloem poles (four white arrowheads). F–G. Truncate midrib: collateral bundles (three white circles), interrupted expansion tissue (ex) with non-linearly arranged fibres (two yellow circles), small accessory vascular bundle within the expansion-tissue caps (green arrowhead), small vascular bundle (white arrowhead), and non-vascular fibres (11 black arrowheads). H. Detail of the accessory vascular bundle: vascular tissue (white circle). I. Uniseriate hypodermis (hy) with thin walls. J. Detail of the collateral bundles: phloem poles (six white arrowheads). Photographs by Bruno F. Sant’Anna-Santos.