The survival of populations of rare plant species may be affected both by total levels of seed production and by inbreeding depression expressed upon self-fertilization. We examined natural seed production and rates of self-fertilization in a Nova Scotian lakeshore population of the globally rare Atlantic Coastal Plain plant, Sabatia kennedyana Fernald (Gentianaceae), and determined the effect of self and cross pollinations on fitness at early plant life stages. Seed production was not limited by natural pollination levels. Furthermore, flowers from which pollinators were excluded produced 66% as many seeds as unprotected, naturally pollinated plants, indicating that substantial seed set can occur in the absence of pollinators. The selfing rate of naturally pollinated flowers was estimated as 21% using the inbreeding depression method. Stage-specific inbreeding depression was 19% at germination, and cumulative inbreeding depression from fertilization through germination was 23%. Seed formation (seeds per fertilized ovule) was correlated with proportional germination suggesting linkage or pleiotropy of genes affecting these two life-history stages. Low, early acting inbreeding depression may result from purging of deleterious mutations in low population times during the post-glacial migration of founders into Nova Scotia from the now submerged Continental Shelf habitat. Alternatively, the inbreeding depression values documented for early developmental stages may underestimate its severity at later stages. Crosses between plants in the study population and those at another lake, four km distant, suffered no decrease in performance (“outbreeding depression”) at these early life stages.

Despite the frequent occurrence of hybridization events between broad-leaved members of the genus Potamogeton, few documented reports and descriptions of these taxa are found in North American pondweed literature. Potamogeton crispus and P. praelongus are common broad-leaved pondweed species with overlapping distributions in North America, yet no confirmed report of their hybrid, P. × undulatus, has been previously documented from this continent. We provide the first confirmed report of P. × undulatus in North America, where it was collected from a northeastern Indiana lake. Because most descriptions of P. × undulatus are found in somewhat less accessible nineteenth century European pondweed literature, morphological characters that are diagnostically valuable in distinguishing the hybrid from its parents are discussed and illustrated. A vegetative key to this hybrid and its parental species is also provided.

Although reported to be essentially glabrous, a hairy ovary summit is characteristic of the fruit of Amelanchier lucida, and this helps to explain some of the variation in its taxonomic treatment by recent authors. In many instances plants would have been identified as A. stolonifera. Flowering material is here described for the first time. The erect racemes have lower pedicels 8–22 mm long, and petals are 6–7.5 mm long and 2.5–3.3 mm wide. At flowering, the leaves are tomentose but towards the end of flowering the thick tomentum is lost from the outer surfaces of the sepals and the larger leaves. Stoloniferous habit, glossy leaves, ascending sepals, and pubescent ovary summit are a distinctive combination of features of A. lucida. A key to the stoloniferous species of Amelanchier in Nova Scotia is included.

The growth and development of plants is determined by both genetic and environmental factors. In this study, path analysis was employed to investigate the magnitude of developmental variation among six quantitative characters associated with growth in 29 pitch pine (Pinus rigida Mill.) families at Walden Woods, Lincoln, Mass. Seedlings were grown for six months in two environments: sand (poor) and sandy loam (better) with four replications under greenhouse conditions. Data were recorded on stem height and weight, crown height and weight, and total height and weight. Data were analyzed using analysis of variance, heritability, and path analysis. Path analysis measures both direct and indirect effects of independent variables on dependent variables through intermediary variables. Hence, it is a powerful approach for evaluating the causal flow of physiological variables among a system of morphological characters during growth and development. Within this single population of pitch pines, significant genotype-environment interaction was found for most characters. Heritability for four characters was greater for families raised in sand than in sandy loam. Path analysis suggested that the physiological resources may be channeled differentially among various quantitative characters in relation to their environments, indicating that the environment modulates not only the development of individual phenotypic traits but also the relationships among these traits in the entire organism. Moreover we found that environmental effects may overwhelm the genetic expression of a given quantitative trait. Knowledge of relative flexibility/plasticity of individual characters in relation to specific environmental resources may be useful toward understanding developmental biology, growth, and reproduction in plants.

The vascular flora of Coneflower Glacial Drift Hill Prairie Natural Area in Moultrie County, east-central Illinois, was studied during the growing seasons of 2002 and 2003. The prairie is located on a steep SW-facing hillside of the Cerro Gordo Glacial Moraine, overlooking the Kaskaskia River Valley and Lake Shelbyville. The flora was documented by general reconnaissance, and the structure of the vegetation was sampled in September 2003 using 0.25 m² plots placed along two transects. The site supported 164 vascular plant species (including one named hybrid). The native grasses with the highest importance values were Andropogon gerardii (big bluestem) and Schizachyrium scoparium (little bluestem). Important forbs included Euphorbia corollata (flowering spurge), Helianthus divaricatus (woodland sunflower), Ratibida pinnata (drooping coneflower), and Comandra umbellata (false toadflax). Exotic species were represented by 28 taxa, 16.4% of the flora. The community had a Floristic Quality Index of 38.82, indicating a site of statewide significance.

A floristic inventory of the remnant pinelands of the U.S.D.A. Subtropical Horticultural Research Station at Chapman Field, Miami-Dade County, Florida was conducted from July 2002 to March 2003. From the two-hectare study site, 159 vascular plant species were documented. These included six ferns and fern allies, two conifers, and 151 angiosperms (representing 49 families and 124 genera). Of the 159 species, 118 are native to North America north of Mexico and 41 are non-native but naturalized. The families with the most species in the study area included Fabaceae (25 spp.), Poaceae (20 spp.), Asteraceae (15 spp.), and Euphorbiaceae (9 spp.). The best-represented genera were Chamaesyce (five spp.), Sida (four spp.), and five genera with three species each: Chamaecrista, Ipomoea, Lantana, Rhynchosia, and Senna. Five species are new records for Miami-Dade County. Ten Florida endemic species, eight Florida threatened species, four Florida endangered species, and one federally listed endangered species were documented.