New data sets and analytic techniques provide the tools to build a new perception of changes in the New England flora following the retreat of the last Pleistocene continental glacier. We consider a set of 13 species for which genetic data are available in the context of 1) the fossil record when available, and 2) the evidence of the distribution of appropriate habitat in the late Pleistocene and Holocene. The current New England flora is derived from a diverse set of refugia including the High Arctic, the serpentines of the American West, and the unglaciated and now submerged North Atlantic coastal plain as well as the traditional refugia to the south, both along the coastal plain and to the west in the lower Mississippi valley. This analysis demonstrates that present-day communities are in fact transient, constantly changing assemblages of species.

The pine barrens in the fall-line sandhills of western Georgia can be accepted as the type locality for Ceranthera linearifolia as described by Stephen Elliott in his Sketch. This remote area between the Chattahoochee and Flint Rivers became accessible in the early 1800s with the building of the Federal Road from Washington, D.C. through Georgia to Mobile, Alabama. Subsequently renamed Dicerandra linearifolia by George Bentham, this new mint genus was among several plants found and described by Elliott along the Federal Road. To establish the type locality, new field collections from the Georgia pine barrens were compared with Elliott's collections sent to Hooker and Schweinitz. A specimen at Kew (k) is designated as the lectotype for C. linearifolia and a new isolectotype is found at Geneva (g). A suite of characters, including strikingly linear leaves with strongly revolute margins, two-flowered cymes and generally unbranched stems, was common to both the types and the new collections from the Georgia pine barrens.

Three new taxa are described from the Arizona Strip in northwestern Arizona: Camissonia dominguez-escalantorum N.D. Atwood, L.C. Higgins & S.L. Welsh, sp. nov.; Physaria arizonica (S. Watson) O'Kane & Al-Shehbaz var. andrusensis N.D. Atwood, S.L. Welsh & L.C. Higgins, var. nov.; and Tetradymia canescens DC. var. thorneae N.D. Atwood, S.L. Welsh & L.C. Higgins, var. nov. Two new taxa are described from New Mexico: Lepidium montanum Nutt. ex Torr. & A. Gray var. todiltoensis N.D. Atwood & S.L. Welsh, var. nov. and Hymenoxys argentea (A. Gray) K.F. Parker var. thoreauensis N.D. Atwood, S.L. Welsh & A. Clifford, var. nov. Two new species are described from Utah: Camissonia bolanderi N.D. Atwood & S.L. Welsh, sp. nov. and Erigeron katiae S.L. Welsh and N.D. Atwood, sp. nov. Each is compared to related species based on differences in morphology.

Variation in ploidy levels in Phragmites australis is a well-documented phenomenon although North American populations are less studied than European ones. It has been suggested, based on morphological measurements, that native and introduced P. australis subspecies in North America represent different ploidy levels. The objectives of this study were to assess whether guard cell size and stomatal density, morphological differences indicative of variation in ploidy level between native and introduced P. australis, are truly associated with different ploidy levels as measured by flow cytometry. Significant differences in guard cell size and stomatal densities were found between subspecies, with native plants having larger guard cells and lower stomatal density. However, no differences in 2C DNA content were found. Although these morphological measurements are significantly correlated with subspecies and can be added to the list of useful morphological characters distinguishing the two subspecies, it does not appear that they are accurate indicators of ploidy levels. Potential implications of these differences on the invasion biology of introduced P. australis are discussed.

Despite a large body of work on the serpentine-substrate effect on vascular plants, little work has been undertaken to describe lichen communities growing on serpentine soils derived from peridotite and other ultramafic rocks. Most such work has been conducted in Europe and western North America. Only one study to date has examined the lichen flora of an ultramafic outcrop in eastern North America. The current paper examines the lichen flora of a peridotite outcrop from Deer Isle, Hancock County, Maine, U.S.A. The lichen flora is presented along with relevant ecological and geochemical data. Sixty-three species were found, comprising 35 genera. Two species, Buellia ocellata and Cladonia symphycarpia, are new reports for New England. Fuscopannaria praetermissa, Psorula rufonigra, and Spilonema revertens are new reports for Maine. Twenty species including one genus, Lobaria, are new reports for ultramafic soils worldwide. Buellia ocellata, P. rufonigra, and S. revertens are reported from several localities on the outcrop. Soil analyses were conducted for pH, electrical conductivity, cation exchange capacity, heavy metals, and cations. Soil pH and cation and heavy metal concentrations are similar to those reported from west coast ultramafic soils suggesting that a similarly strong substrate effect may exist for species present on ultramafic soils in eastern North America.

Two new species of Wikstroemia from Sichuan, China, are described and illustrated. Wikstroemia guanxianensis from Dujiangyan Xian is similar to W. dolichantha in the one-sided development of the disc and in the elongate inflorescence. It differs from W. dolichantha in the oval, wider leaves (to 3.5 cm wide) rounded at the base, longer pedicel (1.5 mm), and disc quadrate, apex truncate, undulate. Wikstroemia jiulongensis is similar to W. fargesii, but differs from it in young branches with scattered pubescence, the peduncles absent or very short, and a quadrate disc with undulate apex. A key to similar species of Wikstroemia in Sichuan is provided.