The Cuticular Epithelium of Bitelaria, an Early Devonian Vascular Plant from New Brunswick, Canada

Abstract

The Early Devonian vascular land plant Bitelaria dubjanskii (Istchenko & Istchenko) Johnson & Gensel has a cuticle that is unusually thick (50-500 μm) and structurally complex. The cuticle consists of cutinized layers and, on some axes (type A), an external humic layer. Although actual cells are not preserved, brown lamellae within the cuticle reflect not only patterns of cellular organization but also patterns of cell division of the surface layer, i.e., of the cells that produced the cuticle. It is demonstrated through observations of microtome thin-sections of the cuticle and comparison of these with external morphology that the three morphological types of Bitelaria axes (types A, B, and C) represent various developmental stages and that this barklike cuticle can be characterized as a cuticular epithelium. This type of cuticular structure in living plants, and probably in Bitelaria, reflects a prolonged period of lateral expansion of primary tissues.