Plant Biology Commons^™

Hybrid Oaks: Full Of Vexation And Wonder, W. John Hayden

Biology Faculty Publications

Distinguishing different species of oak in the forests of eastern North America can be challenging. For one thing, there are simply a lot of different species to sort out. A recent reference (Stein et al. 2003), describes 50 species in the genus Quercusoccurring naturally east of the 100th meridian, and 90 species are distinguished for all of North America north of Mexico (Nixon 1997). With so many species to parse, confident identification requires careful study of leaves, stem and leaf hairiness, and fully mature acorns with their caps. But care is not always enough, because in addition to the …

2011 Wildflower Of The Year: White Oak, Quercus Alba, W. John Hayden

Biology Faculty Publications

Emblematic of strength and longevity, white oaks grace the deciduous forests of eastern North America.

Gender And Species Use In Amazonian Home Gardens: The Social And Economic Context Of Biodiversity Conservation, Leigh Ann West, David S. Salisbury, Ana I. Ríos-Sanchez, Jorge Vela Alvarado

Geography and the Environment Poster Presentations

Home gardens, “the peridomestic area belonging to the household where members plant and/or tend useful plants” (Perrault-Archambault and Coomes 2008), are found throughout the world. However, their use and importance vary from region to region. In the Peruvian Amazon, owners use home gardens for a domestic supply of foods, craft materials, medicines, condiments, and shade (Miller and Nair 2006). With this wide range in function, reflected in species content, home gardens are very biodiverse.

Home garden biodiversity may be increasingly important in a rapidly changing Amazonia (Betts et al. 2008). Thus, the sociocultural and economic factors contributing to home garden …

Don't Judge A Book By Its Cover: The Curious Case Of Wild Ginger Pollination, W. John Hayden

Biology Faculty Publications

What pollinates wild ginger? This seems like an easy question. The inconspicuous little flowers are held close to the forest floor, often completely hidden by a dense canopy of ginger leaves above. Flower color is rather drab, dominated by brown and maroon hues. Wind pollination seems completely unlikely and flowers pollinated by bees, butterflies, moths, or hummingbirds are always much more showy and accessible to these flying creatures. Flies, however, given their natural inclination to seek carrion as a food source for their babies (i.e. maggots), are often attracted to brown and maroon flowers. And because their actual quarry, animal …

2010 Wildflower Of The Year: Wild Ginger, Asarum Canadense, W. John Hayden

Biology Faculty Publications

Wild ginger is a low herbaceous plant. The stem consists of a branched creeping rhizome at or just below the soil surface. Soft-hairy leaves arise in pairs annually from rhizome branches. Petioles can be up to 20 cm long, elevating the 7—25 mm wide kidney-shaped leaf blades above the forest floor. Small flowers appear in the spring shortly after the leaves have expanded. Typically, one must push the leaves aside in order to glimpse the jug-like flowers. A single flower stalk appears between the paired leaf bases, but it is short and barely lifts the flower above the soil surface. …

Hunker Down And Hold On: Contractile Roots Give Skunk Cabbage Another Special Trait, W. John Hayden

Biology Faculty Publications

I can remember the first time I ever heard of contractile roots. It was in graduate school at the University of Maryland and a friend of mine was busy preparing a lecture on roots. He said to me something like “Did you ever notice, while pulling up dandelions, that the darn weed seems to be pulling back? As it turns out, it is!” Strange but true, dandelions, along with a diverse assemblage of other species, have contractile roots that serve to pull the plant downward. In this capacity, contractile roots go well beyond the routine function of providing anchorage for …

2009 Wildflower Of The Year: Skunk Cabbage, Symplocarpus Foetidus, W. John Hayden

Biology Faculty Publications

Skunk cabbage is a coarse herbaceous plant. The stem consists of a stout rhizome oriented vertically in the soil. Leaves and flowers arise from the tip of the rhizome which is often not visible, resulting in the appearance of leaves and flowers arising directly from the swampy mires where these plants grow. Flowers appear during the winter, long before the leaves. The flowers are minute, clustered into a ball-like group (spadix) almost entirely enclosed by a fleshy, hood-like, spathe. The spathe ranges from 8 to 15 cm in height, is more or less pear-shaped, widest near the bottom, and tapers …

Skunk Cabbage Flowers: The Heat Is On, W. John Hayden

Biology Faculty Publications

It is a remarkable sight, as striking as it is unexpected: January skunk cabbages emerging from the frozen mires they call home, melting their way through snow and ice. It seems so improbable because in everyday experience plants exist at equilibrium with ambient temperatures. Leave an apple on the front seat of your car in summer, it gets hot; examine your tomato plants on that first frosty morning in autumn, and they are permeated with ice crystals. People, mammals and birds are inherently warm, and pretty much nothing else is. Except, of course, for the exceptions, of which skunk cabbage …

Spiderworts: Not Just Another Pretty Face For Science, W. John Hayden

Biology Faculty Publications

Species of Tradescantia, or spiderworts, are handsome plants. Several wild species, including the VNPS wildflower of the Year for 2008 (T. virginiana), can be found in eastern North America and additional species grace gardens, and hothouse conservatories. Spiderworts are not, however, just a bunch of pretty faces. Spiderworts have a long history of service to science, both in terms of teaching and pure research.

Spiderwort Is Vnps Wildflower Of The Year, W. John Hayden

Biology Faculty Publications

The VNPS 2008 Wildflower of the Year (WOY) is spiderwort (Tradescantia virginiana). This herbaceous perennial plant occurs throughout much of the eastern portion of the U.S. and is widespread in Virginia. Spiderwort blooms from April to July. The small flowers occur in clusters at the ends of the stems, atop several elongate bracts. Flowers have three petals that range from purple to rose or, rarely, white. Densely hairy stamens provide, perhaps, the easiest way to recognize spiderworts. Also, stalks of spent flowers droop below the flower cluster yielding an aspect reminiscent of spindly spider legs.

2008 Wildflower Of The Year: Virginia Spiderwort, Tradescantia Virginiana, W. John Hayden

Biology Faculty Publications

Spiderwort is an herbaceous perennial that arises from a cluster of rather stout overwintering roots. Stems may be solitary or more commonly clumped, and usually grow unbranched, reaching heights up to 40 cm tall. Stems are smooth or bear scattered short hairs. Leaves are 2—5 per stem, attached by means of a leaf sheath that is 13 cm long. Leaf blades are dull green, elongate, ending in a gradually tapered tip, flat or keeled, smooth (without hairs), and 1—3.5 dm long by 0.5—2.5 cm wide. Flowers occur in tight clusters located at the stem apex; bracts similar to the leaves …

Atamasco Lily, Zephyranthes Atamasca, W. John Hayden

Biology Faculty Publications

Simple and pure, Atamasco lilies were among the first of many beautiful wildflowers to be noticed by the Jamestown colonists as they explored the tidewater region of southeastern Virginia. A perennial herb that grows from a subterranean bulb, the leaves are glossy green, linear, flat to somewhat concave, up to one half inch wide and approximately one foot in length. The species name, atamasca, is attributed to Tapehanek words meaning under grass, in reference to the location of the bulb under grass-like leaves. Overall the plant is rather grass-like. Flowers are erect to slightly inclined. As in many lilies, …

Zephyr Lilies: Simple Beauty Belies Complex Biology, W. John Hayden

Biology Faculty Publications

It is often thus, the best in art appears effortless; the most compelling science, once understood, seems obvious. But talk at length with any artist or scientist and you will learn that what appears simple is actually the culmination of a great deal of work. Zephyr, or Jamestown, lilies are like that, too. These seemingly simple flowers are merely the elegant end product of some very complex underlying biology, the details of which are imperfectly understood.

Are Hawkmoths The Mysterious Pollinators Of The Jamestown Lily?, W. John Hayden

Biology Faculty Publications

“Hawkmoth flowers are easy to predict but difficult to document,” noted botanist Verne Grant in his comprehensive review of hawkmoth pollination systems in North America (Botanical Gazette 144: 439-449. 1983). Grant included Jamestown (atamasco) lilies (among other zephyr lily species) as examples of plants that are probably hawkmoth- pollinated, but for which the actual pollination mechanism remains undocumented.

2007 Wildflower Of The Year: Atamasco Lily, Zephyranthes Atamasca, W. John Hayden

Biology Faculty Publications

Atamasco lily is a perennial herb that grows from a subterranean bulb. The bulb is dark, with a short neck and papery tunic formed by remnants of old leaf bases. Leaves are glossy green, linear, flat to somewhat concave, up to one half inch wide, approximately one foot in length and, overall, rather grasslike. When not in flower the plants can be easily overlooked. Flowering stems are leafless scapes that are about as long as the leaves. In crosssection the scapes are hollow. Each scape terminates in a single flower. A few papery bracts subtend the flower stalk where it …

2006 Wildflower Of The Year: Spicebush, Lindera Benzoin, W. John Hayden

Biology Faculty Publications

Spicebush is a multistemmed deciduous shrub that grows to a height of one to three meters. Young stems are delicate and may be smooth or finely hairy. Leaves are alternate and simple, with an elliptic to obovate blade that tapers at both the base and apex and is bounded by a smooth margin. Examined closely, the margin will reveal a series of fine hairs that project directly out from the leaf edge. In size, leaves are neither remarkably large nor small; they range from one to six inches in length and up to about two and a half inches wide, …

Bloodroot Pollination: Bet-Hedging In Uncertain Times, W. John Hayden

Biology Faculty Publications

“Hurry up and wait.” The phrase that epitomizes life in the military or any other large, bureaucratic, organization, applies surprisingly well to bloodroot and similar ephemeral wildflowers. Each year these plants race to flower as early as possible to assure sufficient time for fruits to ripen and seeds to mature while sunshine is abundant at the forest floor, for all too soon the forest floor will be draped in shadows cast by the trees’ leafy canopy. Ephemerals do everything quickly: sprout, grow, flower, disperse seeds, and re-enter dormancy. But flowering in very early spring can be risky. Some days will …

2005 Virginia Wildflower Of The Year: Bloodroot, Sanguinaria Canadensis, W. John Hayden

Biology Faculty Publications

Bloodroot is an herbaceous perennial that grows from a persistent, branched underground stem or rhizome. Early each spring, while the forest canopy is still bare, each well-developed rhizome tip produces one leaf and one flower stalk. The leaf is kidney-shaped in its overall outline, but it is also divided into a pattern of rounded lobes and sinuses, rendering a complex overall shape. At flowering time, bloodroot leaves form a loose vertically-oriented collar around the flower stalk with the bluish-green lower leaf surface forming the outside of the collar; as the season progresses, the leaves open flat and expand to their …

Amanoa, W. John Hayden

Biology Faculty Publications

Monoecious or dioecious trees or shrubs, latex absent. Leaves alternate, distichous, evergreen, simple, coriaceous, glabrous; stipules intrapetiolar, paired, or confluent across the leaf axil; margins entire; venation pinnate. Inflorescence axillary and/or terminal, of densely bracteate clusters (reduced cymules), in the axils of ordinary foliage leaves, in nonleafy pseudoterminal aggregates that revert to vegetative growth, or (in neotropical species) in the axils of alternate, reduced, crescentiform stipular bracts of determinate deciduous spiciform axes borne in groups of 1-several per branch apex; axes straight or sinuous; floral bracts minute, deltate, with abaxially pubescent midribs. Staminate flowers sessile or pedicellate, regular; perianth biseriate; …

Seedling Development In Species Of Chamaesyce (Euphorbiaceae) With Erect Growth Habits, W. John Hayden, Olga Troyanskaya

Biology Faculty Publications

Seedling development is described for Chamaesyce hirta, C. hypericifolia, and C. mesembrianthemifolia as discerned by light microscopy and scanning electron microscopy. Although these species ultimately develop erect to ascending growth habits, epicotyl development is limited to the production of a single pair ofleaves located immediately superjacent to and decussate with the cotyledons. The shoot system develops from one or more buds located in the axils of the cotyledons. In all respects, seedling ontogeny is very similar to that of previously studied prostrate species of Chamaesyce. Evidence from seedling ontogeny thus contradicts a hypothesis concerning homologies of plant …

Revision Of The Cerrado Hemicryptophytic Chamaesyce Of Boissier's "Pleiadeniae" (Euphorbiaceae), Mark P. Simmons, W. John Hayden

Biology Faculty Publications

The species of Chamaesyce classified by Boissier as the "Pleiadeniae'" are revised in light of presently available collections. Six species are accepted and new combinations are proposed for C. nana, C. setosa, C. tamanduana, and C. viscoides. Although these herbaceous perennials of cerrado vegetation of Brazil, northern Argentina, and adjacent countries are distinctive ecologically and geographically, cladistic analysis does not support their recognition as a monophyletic group.

Taking Root, W. John Hayden

Biology Faculty Publications

The brief description of mangrove reproduction in John N. Cole's "Off Key, Out of Reach" [A Sense of Place, July-August] contains an error.

A Revision Of Discocarpus (Euphorbiaceae), Sheila M. Hayden, W. John Hayden

Biology Faculty Publications

As revised here, Discocarpus is interpreted to consist of three neotropical species: D. essequeboensis Klotzsch, D. gentryi S. M. Hayden, which is described and named herein as new to science, and D. spruceanus Müll. Arg. One previously accepted name, D. brasiliensis Klotzsch ex Müll. Arg., is reduced to synonymy of D. essequeboensis. Lecto-types are proposed for the two species previously described. One species is newly excluded from Discocarpus, as are three others, following previous literature. Foliar anatomy is described with a focus on epidermal sclereids, which are shown to occur on both epidermides. Evidence presented supports close relationships …

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 …

Mistaken Identity?, W. John Hayden

Biology Faculty Publications

The December 1994 NEWS item "Red Menace" contains, I believe, an unfortunate misidentification of the algae allegedly responsible for the catastrophic mortality of sea birds from Pliocene deposits of the Florida Gulf Coast.

Systematic Anatomy Of Euphorbiaceae Subfamily Oldfieldioideae I. Overview, W. John Hayden

Biology Faculty Publications

The biovulate subfamily Oldfieldioideae of Euphorbiaceae, characterized by spiny pollen, is an otherwise apparently diverse assemblage of mostly Southern Hemisphere trees and shrubs that traditionally have been allied with genera of Phyllanthoideae and Porantheroideae sensu Pax and Hoffmann. Although fairly diverse anatomically, the following structures characterize the subfamily with only a few exceptions: pinnate brochidodromous venation with generally randomly organized tertiary and higher order venation; foliar and petiolar glands absent; unicellular or unbranched uniseriate trichomes; latex absent; mucilaginous epidermis or hypodermis; brachyparacytic stomata; vessel elements with simple perforation plates and alternate, often very small, intervascular pits; thick-walled nonseptate imperforate tracheary …

Stem Development, Medullary Bundles, And Wood Anatomy Of Croton Glandulosus Var. Septentrionalis (Euphorbiaceae), Sheila M. Hayden, W. John Hayden

Biology Faculty Publications

Anatomy and development of vascular tissues in the annual stems of Croton glandulosus var. septentrionalis are described. In primary stages of growth the stem possesses a eustele of bicollateral bundles; international phloem is notably more extensive than the external. In addition to a vascular cambium and secondary xylem that form in the usual fashion, additional cambia add cells to the internal phloem portion of the bicollateral bundles, forming well-marked medullary bundles at the perimeter of the pith. At first, the perimedullary cambial strands produce only internal secondary phloem; later, internal secondary xylem is present, the medullary bundles have an inverted …

Wood Anatomy Of Amanoa (Euphorbiaceae), W. John Hayden, Mark P. Simmons, Linda J. Swanson

Biology Faculty Publications

Wood anatomy of 29 specimens of seven species of Amanoa from tropical Africa, South America, and the Caribbean is described. The wood is diffuse-porous with most vessels in short radical multiples. Vessel elements are notably long, have simple perforation plates and small, alternative intervessel pits; tyloses are present in heartwood. Libriform wood fibres bear thick walls. Axial parenchyma distribution is diffuse and diffuse-in-aggregates. Chambered crystalliferous axial parenchyma is common. Rays are heterocellular, narrow, and very tall. The species examined, all from moist lowland forests, have similar wood structure. Wood of Amanoa resembles that of other primitive Euphorbiaceae.

A Survey Of Mucilaginous Testa In Chamaesyce, Martha S. Jordan, W. John Hayden

Biology Faculty Publications

Seeds of Chamaesyce were studied for presence of mucilaginous testa. Samples were selected to represent all major systematic sections within the genus. Observations were made with a dissecting microscope following brief hydration of seeds; additional SEM observations of both intact and fractured dry seeds were made for selected species. With few exceptions, most of Boissier's subsections test positively for seed mucilage; however, mucilage is generally absent in subsections Gymnadeniae and "Sclerophyllae", for which absence of mucilage is regarded as secondary loss from mucilagionus ancestors. Although mucilage production is associated with a well-defined subepidermal layer of macroesclereids, it is …

Notes On Neotropical Amanoa (Euphorbiaceae), W. John Hayden

Biology Faculty Publications

Lectotypes are designated for Amanoa caribaea Krug & Urban and A. guianensis Aublet; presumed syntypes of the latter taxon are shown to be heterogeneous by inclusion of a previously unrecognized species. Four new species of Amanoa are described: A. congesta from French Guiana and northeastern Brazil; A. gracillima from Manaus, Brazil; A. nanayensis from Amazonian Peru and adjacent Colombia and Brazil; and A. neglecta from French Guiana and Surinam. Amanoa sinuosa is proposed as a new name for the later homonym A. robusta Leal. A key to the 13 neotropical species is presented.