Atlas of Foliar Surface Features in Woody Plants, V. Fraxinus (Oleaceae) of Eastern North America

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Abstract
Scanning electron microscopy of foliar surfaces of the seven species ofFraxinus native in eastern North America confirms the importance of cuticular patterns (smooth, striated, striate-papillose, and coronulate) as useful taxonomic character states. There are there trichome types (acicular hairs ornamented with micro-striae or-papillae, peltate glands, and scales) which are found in nearly all species and which vary only in density. No differences in surface features are found by which determination can be made of either sex or ploidy level inF. americana. Hybridization betweenF. americana andF. pennsylvanica is considered to be rare in nature and is not a probable cause for the overlap of character states and concomitant difficulty of identification based upon gross morphological features. Likewise, the putative hybrid origins ofF. biltmoreana andF. profunda are not supported by micro-morphological features. Illustrations are given for all species.