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Unique Features Of Caenothus Trace To Earliest Stages Of Flower Development, W. John Hayden
Unique Features Of Caenothus Trace To Earliest Stages Of Flower Development, W. John Hayden
Biology Faculty Publications
The basics of flower structure are straightforward. A “typical” flower (Figure 1) has four whorls of floral organs arranged in stereotypical order: sepals (lowermost and outermost), petals, stamens, and, finally, one or more carpels (pistils) located in the innermost (or uppermost) position. This is not rocket science. Names of these floral organs and their relative placement within the flower can be grasped readily by schoolchildren. Also “typical” but seldom emphasized in elementary lessons is the fact that the organs of each successive whorl occupy alternate radii; i.e., petals are routinely positioned between sepals, and stamens (if only one whorl) are …
Redbud Seedpods Hold Surprises, W. John Hayden
Redbud Seedpods Hold Surprises, W. John Hayden
Biology Faculty Publications
As fall advances across the Old Dominion, canopies of redbud, the 2013 VNPS Wildflower of the Year, transform themselves from green to gold, revealing seed pods also changing color from pale green to dark chocolaty brown. These seedpods, which may be retained on the tree into winter, are typical legume fruits, the product of the flower’s simple pistil, each containing several seeds. Unlike most legumes, however, redbud seed pods seem disinclined to open and release individual seeds for dispersal. Redbud fruits tend to disperse intact. Once on the ground, the inevitable action of weather and microbes gradually degrades the pod, …
Redbuds Similar Around The World, W. John Hayden
Redbuds Similar Around The World, W. John Hayden
Biology Faculty Publications
Like music, one of the hallmarks of biodiversity is theme and variation. Redbuds—species of the genus Cercis— from around the world illustrate this analogy well. Because all redbud species conform to a certain morphological theme, anyone familiar with one particular species of redbud should be able to recognize without hesitation any other redbud species as a member of the genus Cercis. In brief, the redbud theme consists of broad, basally-lobed, leaves with pulvinar petiole thickenings, and pea-like red-purple (rarely white) flowers that may arise on small twigs or main trunks. In fact, these plants are so distinctive, it would …
Redbuds And Legumes Subfamilies, W. John Hayden
Redbuds And Legumes Subfamilies, W. John Hayden
Biology Faculty Publications
Although legumes constitute one of the largest families of flowering plants in the world, and despite 25 years of celebrating Virginia’s wildflowers, redbud (Cercis canadensis) is the first legume to be recognized as a VNPS Wildflower of the Year. This article addresses the relationships of Cercis with the rest of the legumes (family Fabaceae, or Leguminosae in older literature).
White Oak Part Of Global Oak Presence, W. John Hayden
White Oak Part Of Global Oak Presence, W. John Hayden
Biology Faculty Publications
As we act locally celebrating white oak, Quercus alba, as the 2011 VNPS Wildflower of the Year, it is perhaps appropriate to think globally for a few moments and consider the breadth of diversity encompassed by the oaks. Quercus is a big genus, easily the largest in its family, the Fagaceae. Approximately 400 species of oak are known, and they are widely distributed in the northern hemisphere. We tend to think of oaks as temperate zone trees, but in the New World, their range extends south through the mountains of Central America to Colombia and in the Old World, …
The Vascular Flora Of The Potomac River Watershed Of King George County, Virginia, Mark P. Simmons, Donna M.E. Ware, W. John Hayden
The Vascular Flora Of The Potomac River Watershed Of King George County, Virginia, Mark P. Simmons, Donna M.E. Ware, W. John Hayden
Biology Faculty Publications
The results of two floristic studies of King George County, Virginia, are combined into an annotated checklist. Field work was initiated in 1983-84 with a study of Caledon Natural Area, a 2,500-acre tract with 3.5 miles of frontage on the Potomac River. Collecting resumed in 1991 and 1992 to include other portions of the county drained by the Potomac River. The study area contains a wide variety of habitats including dry upland woods, mesic ravines, low elevation river flats, beaches, swamps, marshes, and creeks; creeks and marshes include both brackish and freshwater environments. The Potomac River watershed of King George …
Methyl Salicylate Secretory Cells In Roots Of Viola Arvensis And V. Rafinesquii (Violaceae), W. John Hayden, John Clough
Methyl Salicylate Secretory Cells In Roots Of Viola Arvensis And V. Rafinesquii (Violaceae), W. John Hayden, John Clough
Biology Faculty Publications
The aromatic roots of Viola arvensis and V. rafinesquii were studied in order to determine the chemical nature and anatomical localization of their volatile compounds. Gas chromatography and mass spectroscopy revealed a single detectable volatile compound, methyl salicylate. Light microscopy and differential staining with Sudan III indicates the source of this compound to be enlarged secretory cells located in the endodermis, an unusual position for such cells in roots of angiosperms. The secretory endodermal cells are sporadic, but are more frequent in primary roots than in secondary roots and the lower portion of the hypocotyl. It is hypothesized that …
Flueggea Willd, W. John Hayden
Flueggea Willd, W. John Hayden
Biology Faculty Publications
Shrubs to large trees with watery sap. Leaves simple, alternate, pinnately veined, stipulate. Flowers unisexual (and the plants dioecious or rarely monoecious), actinomorphic, in axillary clusters; sepals 4-7, imbricate; petals absent; nectary disk lobed or entire; stamens (3)4-7, alternate with the lobes of floral disk, staminodes absent in pistillate flowers; filaments distinct; ovary superior, on a hypogynous disk, (2)3(4)-carpellate, ovules 2 per cell, hemitropous, pistillode present in staminate flowers; styles distinct and 2-lobed or stigmas sessile. Fruit a capsule or baccate, indehiscent. Seeds 2 per cell. [Hayden, 1987; Sherff, 1939b]
The Identity Of The Genus Neowawraea (Euphorbiaceae), W. John Hayden
The Identity Of The Genus Neowawraea (Euphorbiaceae), W. John Hayden
Biology Faculty Publications
On the basis of newly acquired morphological evidence gathered in the course of floristic studies, the monotypic genus Neowawraea Rock is now recognized as a species of Flueggea Willd. and is renamed F. neowawraea W. J. Hayden. Taxonomic documentation presented for F. neowawraea includes an expanded morphological description, a map showing its widely scattered distribution in the Hawaiian Islands to which the species is endemic, and discussions of type specimens, common names, and its extreme rarity. The combination of flowers in pedicellate axillary clusters, the lobed staminate disk, pistillode, extrorse anthers, hemitropous ovules, and, especially, the smoothish dry seeds with …