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The pollen of three Ephedra taxa, Ephedra torreyana, E. trifurca and E. funerealeft right double arrowE. torreyana, showed a marked pollen dimorphism when examined using scanning electron microscopy. Typical pollen grains in all of these taxa have straight ridges, but the variant forms exhibit a highly folded ectexine. In addition, previously used characters such as the presence or absence of bifurcating valley structure do not appear to be uniform, even within a single microsporangium, suggesting that their value to taxonomic study should be reassessed. Published in Review of Palaeobotany and Palynology, volume 124, issue 3-4, on pages 325 - 334, in 2003.
Pollen ratios and linear discriminant analysis were used to detect fine-scale vegetation patterns in the subalpine zone of the central Rocky Mountains, USA. The vegetation of this zone is a mosaic of conifer forests and treeless parks dominated by sagebrush (Artemisia spp.) and grasses. Previous work with pollen surface samples in the region has correlated modern pollen rain to broad-scale vegetation zones (e.g. steppe, montane forest, subalpine forest, and tundra), but little effort has been made to detect fine-scale (hundreds to thousands of meters) patterns within these vegetation zones. Previous theoretical studies suggest that vegetation patterns on the scale of hundreds of meters should be recorded in the...
An extinct genus of the Polemoniaceae is described from one complete fossil plant preserved in shale of the Eocene Green River Formation, Utah. Combined vegetative and reproductive characters including the taproot, basal and cauline pinnatifid leaves, primary peduncular leaves, secondary peduncular bracts, pedicel bracts, fruits in groups of three, and persistent calyx, support placement of this plant close to the extant genus Gilia. Gilisenium hueberi gen. et sp. nov. represents a rare record of an herbaceous plant, and the oldest megafossil for the family Polemoniaceae. Published in Review of Palaeobotany and Palynology, volume 104, issue 1, on pages 39 - 49, in 1998.
The purported ash samara, Fraxinus flexifolia (Lesquereux) Brown (1940) from the middle Eocene Green River Formation, is shown to be the same as small inequilateral legume leaflets identified as Mimosites coloradensis Knowlton. Because the name Mimosites Bowerbank is restricted to legume pods with mimosoid affinities, the new combination Parvileguminophyllum coloradensis (Knowlton) Call and Dilcher is proposed for the previously supposed samara, here recognized as a leaflet, and for leaflets currently placed in M. coloradensis. A lectotype is designated from among Knowlton's original specimens. The transfer of Brown's so-called Fraxinus samara to Parvileguminophyllum coloradensis (Knowlton) Call and Dilcher comb....