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Sida, Contributions To Botany


Schoenoplectus hallii (A. Gray) S.G. Smith (Cyperaceae), a rare plant restricted to wetland habitats, is of conservation concern throughout its range. Taxonomy of the species recently has been clarified; however, quantitative descriptions of achene and flower morphology are incomplete and life history information is lacking. Because of its scarcity and the transient nature of populations, any large-scale study of the species will require the recovery of achenes from bulk soil samples and the identification and separation of the dimorphic achenes. The objectives of this study were to separate, identify and photograph the two achene types; to quantify the size and morphological differences that will be useful in separating terminal and basal achenes; and to determine the range of variability in style morphology and achene size within and among 12 populations in four states. Although each achene type varies significantly in size among populations, size differences between terminal and basal achenes are statistically significant, and the range of sizes within each achene type is larger than has been previously reported. Terminal achenes are significantly smaller in length, width, beak length, mass and surface area than basal achenes, and noticeable differences occur in surface ridging. Differences in style morphology are distinct: terminal flower styles are predominantly bifid and consistent in shape, while basal flower styles, which are six times longer than terminal styles, are trifid with a wide variety of branching patterns. Terminal and basal achenes can be separated accurately and conveniently from bulk soil samples using a series of soil sieves. The visual and quantitative descriptions provided in this study will facilitate the collection and identification of terminal and basal achenes of S. hallii from plants, soil and wildlife.

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