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Physaria ludoviciana (Brassicaceae) is rare in Illinois, Minnesota, and Wisconsin. Environmental effects on floral development are unclear. Both self-compatibility and self-incompatibility occur within Physaria species. Objectives were to describe flowers, to determine how photoperiod affects flower development, and to predict whether flowers are self-compatible or self-incompatible. For photoperiods, greenhouse-grown plants were placed in either 16 or 8 hr photoperiods. Inflorescences and open flowers were counted weekly. For pollination, flowers were self-pollinated or cross-pollinated. Plants developed inflorescences after 20 and 28 d in long and short days, respectively. Inflorescences/plant increased for both photoperiods throughout the study. In short days, plants produced more inflorescences (10.8/plant) than in long days (7.1/plant). Anthesis started at 48 and 56 d for long and short days, respectively. Blooming peaked at 83 d (4.9 flowers/plant/day) for long days, and at 98 d (3.5 flowers/plant/day) for short days. Cross-pollinated flowers produced fruits, while self-pollinated ones did not.
Powhatan County is a largely rural county of the Virginia piedmont currently experiencing exurban development pressure. Commercial pine forests occupy much of the land area; most natural vegetation occurs in various hardwood forests. Plant life is supported largely by soils derived from Proterozoic to Paleozoic metamorphic and igneous rocks, soils developed over Triassic basins, and riparian soils associated with the James and Appomattox Rivers. The annotated checklist is based on new collections gathered between September 2003 and August 2005, supplemented with records from regional herbaria and the Atlas of the Virginia Flora. Field work sampled at least 12 distinct community groups recognized in Virginia. The checklist contains 1020 taxa (1013 species, 515 genera, and 146 families). Twenty-one percent of the species are naturalized introductions. Twenty five species (2.5% of the total) are of conservation concern, and 118 collections (12% of the total) represent new records for Powhatan County.
In Pennsylvania, Dodecatheon inhabits upland woods and wooded rock outcrops in the Potomac and Susquehanna watersheds, respectively. We marked 60 randomly selected plants in each of six Potomac and eight Susquehanna populations. We assessed 20 characters in these plants in flower and fruit to clarify whether they represent D. meadia or D. amethystinum, both of which had been reported for Pennsylvania. The populations differ, often significantly, in the means of all characters; but they overlap in the ranges. For example, corolla color varies from dark to pale pink in all populations. The Potomac population means are greater than the Susquehanna means in scape dimensions, flower number, floral calyx lobe length, anther length, and capsule wall thickness. In the Potomac populations, mean capsule wall thickness is intermediate between the ranges reported by previous authors for the two species. In the Susquehanna populations, this feature resembles the values reported for D. amethystinum.