Surface Features of Quillwort (Isoetes, Isoetaceae, Lycophyta) Microspores Lytton John Musselman, Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529-0266 Traditionally, the surface features of Isoetes megaspores have provided the foundation for determining species. Microspores, on the other hand, have been largely neglected in taxonomic schemes and no descriptors for ornamentation have been widely used other than spinulose, papillate, tuberculate, and smooth. Using species from Africa, Asia, Australia, Europe, and North and South America, I examined microspore ornamentation with the scanning electron microscope. Ornamentation and sculpturing of microspores are more diverse than previously reported. Aculate, cristate, echinate, rugulate, and verrucate macro-ornamentation were found in different taxa. Bacillate and fimbriate micro-ornamentation characterize a diversity of species. Surface features vary on the three faces of the microspore (two proximal, one distal surface, and the single ridge). Based on this limited sampling, species with higher ploidy level have larger microspores but no clear relationship between microspore ornamentation and ploidy level was established nor were any geographical or ecological trends clear. Species with unornamented or psilate microspores are few and reports of this trait could be due to examination of immature spores. Like megaspores, microspores of hybrids are polymorphic, varying both in size and sculpturing.

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