Abstract

Morphological features of seeds of Eucnide and species of subfamily Loasoideae, in- cluding the genera Blumenbachia, Cajophora, Loasa, Sclerothrix, and Scyphanthus, were examined to better understand relationships among Loasaceae. Seeds of Eucnide are bipolar with the hilum at one pole. They are essentially cylindrical with a radial transectional symmetry. Longitudinal ridges extend between the poles of each seed. The seed surface is also characterized by irregular granu- lations that may be large and rough, small and fine, or even largely indistinct, depending upon the species. As has been reported for other loasaceous genera, morphological features of seeds of Eucnide are generally conservative at the sectional level. Differences at the sectional level include size, shape, and secondary surface sculpture. Examination of herbarium collections has shown that E. hirta is more morphologically diverse than other species of Eucnide. Secondary surface sculpture of seeds is used to support the proposition that E. pringlei, recently considered conspecific with E. hirta, is a distinct species. Seeds of a disjunct population of E. hypomalaca have been valuable for showing potential evolutionary relationships between this species and E. pringlei and E. cordata. Seeds of Eucnide sect. Sympetaleia are, perhaps, paedomorphic derivatives of an ancestor with a seed morphology similar to that currently presently in E. bartonioides. Among examined species of subfam- ily Loasoideae, seeds appear primarily to have reticulate surface sculpturing. This reticulate pattern may be a plesiomorphic condition of the family shared by certain sections of various genera of subfamily Loasoideae and Mentzelia (subfamily Mentzelioideae). Seeds of Loasa sect. Huidobria have a surface sculpture composed of longitudinal ridges or folds that superficially cause seeds of these species to resemble those of Eucnide. Certain realignments of species of Cajophora with other genera in subfamily Loasoideae that were suggested by Poston do not seem necessarily appropriate based on data of seed structures reported in her study and this one. Seed morphology has proven to be a valuable feature in many systematic studies, particularly with the application of scanning electron mi- croscopy (SEM) (e.g., Hill 1976; Matthews and Levins 1986). This study focuses on seed mor- phology of Eucnide, although other Loasaceae are also investigated. Hill's (1976) SEM inves- tigation of Mentzelia showed that seed mor- phology was valuable for establishing subge- neric alliances in Mentzelia. Poston (1979) suggested that seed morphology in subfamilies Loasoideae and Mentzelioideae may be conser- vative within subgeneric sections. These two investigations indicate that seeds may provide valuable characters for elucidating macroevo- lutionary relationships among Loasaceae. Prigge (1986) emphasized the important role of seed morphological distinctions for understanding species-level differences in Mentzelia in which recognition of species differences often requires subtle differentiation among characters. The goal of this study is to use seed morpho- logical data to elucidate evolutionary patter:

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