Spore ornamentation in the Dryopteris spinulosa complex

Abstract

The spores of five taxa of North American Dryopteris were studied with the scanning electron microscope. The taxa considered were two eastern diploids, D. intermedia (Muhl. ex Willd.) A. Gray and the eastern diploid of D. "dilatata”; two tetraploids, D. spinulosa (O. F. Muell.) Watt and D. campyloptera Clarkson; and one western diploid, D. assimilis S. Walker. All the taxa have spores with spines. Spine density and spine morphology are variable both within and between taxa and do not allow a clear identification of taxa using these characters alone. It is considered that all five taxa are closely related as evidenced by the similarities in their perine morphology as compared with species outside the complex.