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Research Projects - W. John Hayden

Past to Present, in Approximate Chronological Order

Picrodendron - This small tree, known to some as the Jamaica Walnut occurs on coastal limestones of Cuba, Hispaniola, Jamaica, and some of the Cayman and Bahama Islands. Its first appearance in the scientific literature dates to the late 17th century when Sir Hans Sloane wrote a brief account of it from his experiences in Jamaica. Sloane suggested relationships with Juglandaceae and various botanists over the centuries have made their own suggestions, ranging from assignment in three different genera and some nine different families. My master's thesis at the University of Maryland included a detailed review of the botanical history of Picrodendron, a thorough description of the anatomical structure of its leaves, nodes, and wood, and a discussion of relationships. I concluded that the anatomical and morphological evidence confirmed contemporary palynological work, indicating placement in Euphorbiaceae, subfamily Oldfieldioideae. I've been studying euphorbs ever since--it was this plant that set the hook!

Hayden, W. J. 1977. Comparative anatomy and systematics of Picrodendron, genus incertae sedis. J. Arnold Arbor. 53: 257-279.

Hayden, W. J., & J. L. Reveal. 1980. Proposal for the conservation of the generic name Picrodendron Grisebach (1859) against Picrodendron Planchon (1846) (Euphorbiaceae). Taxon 29: 507-511.

Hayden, W. J., W. T. Gillis, D. E. Stone, C. R. Broome, & G. L. Webster. 1984. Systematics and palynology of Picrodendron: further evidence for relationship with Oldfieldioideae (Euphorbiaceae). J. Arnold Arbor. 65: 105-127.

Oldfieldioideae - wood and leaf anatomy - My doctoral dissertation research (University of Maryland) was a natural extension of my masters project. As noted above, my work on the enigmatic genus Picrodendron suggested that it should be classified in this subfamily. Since I had only examined only a few specimens of Oldfieldioideae, and since the subfamily seemed to consist of an odd assemblage of taxa strewn across the former continental land mass of Gondwana, I thought that a thorough survey would prove interesting. Results suggest that the subfamily is indeed anatomically distinct from subfamily Phyllanthoideae, within which most oldfieldioid genera had been classified previously. Moreover, Oldfieldioideae was found to consist of two major clades, one from Africa and South America consisting largely of taxa with compound leaves, and the other, with simple leaves, centered in Australasia. In addition, several other genera appear to form an ill-defined basal cluster within the subfamily.

Hayden, W. J. 1992. Wood anatomy and relationships of Australasian Oldfieldioideae (Euphorbiaceae). Presented at symposium on "Diversity of Pacific Basin Woods in Past, Present, and Future," sponsored by the National Tropical Botanical Garden, Lawai, Hawaii, and the International Association of Wood Anatomists.

Hayden, W. J. 1994. Systematic anatomy of Oldfieldioideae (Euphorbiaceae). I. Overview. Ann. Missouri Bot. Gard. 81: 180--202.

Neowawraea - While preparing various wood specimens from Phyllanthoideae for comparison with oldfieldioid woods, I happened to section a specimen of Drypetes phyllanthoides from the Hawaiian Islands. This plant had been originally discovered by Joseph Rock and named Neowawraea phyllanthoides, but it had been re-classified as a species of Drypetes by Earl Edward Sherff. I had sectioned numerous woods from other species of Drypetes before and all were hard, flinty, and technically difficult to convert into permanent microscope slides. Drypetes (Neowawraea) phyllanthoides was totally different. It cut like butter and was a breeze to process. Not surprisingly, its wood structure proved to be completely different from every other Drypetes, which is what an honors student (see citations) helped me to do in my early years at UR. We concluded that this plant was better better returned to the genus Neowawraea. When I presented this study at a joint session of ASPT and BSA, I was approached by a botanist then working on a revision of the Hawaiian flora. It seems an amateur botanist in Hawaii had just secured the first ever collection of pistillate flowers of Neowawraea and he offered to let me study them, especially if I would agree to write up the genus for his flora project. I agreed on the spot, thus initiating phase two of my adventures with Neowawraea, focused largely on herbarium specimens and the newly obtained pistillate flowers. Sheila Hayden provided me with the first ever technical illustration of the plant and after taking a single glance at her drawings, a colleague made the seminal suggestion that Neowawraea looked an awful lot like plants in the genus Flueggea. As it turned out, Neowawraea shared a distinctive pit in the seed coat known elsewhere in the euphorbs only among species of Flueggea. Clearly, Neowawraea phyllanthoides was in reality a species of Flueggea. Since the name Flueggea phyllanthoides had already been published for yet another plant, the Hawaiian entity became known as Flueggea neowawraea W. J. Hayden. Flueggea neowawraea is extremely rare and in danger of extinction.

Brandt, D. S., & W. J. Hayden. 1983. Wood anatomy and relationships of the Hawaiian endemic genus Neowawraea (Euphorbiaceae). Virginia Academy of Science Annual Meeting, Fairfax, Virginia. ABSTRACT: Virginia J. Sci. 34: 138.

Hayden, W. J., & D. S. Brandt. 1984. Wood anatomy and relationships of Neowawraea (Euphorbiaceae). A.I.B.S. Annual Meeting, Fort Collins, Colorado. ABSTRACT: Amer. J. Bot. 71(no.5, part 2): 170.

Hayden, W. J., & D. S. Brandt. 1984. Wood anatomy and relationships of Neowawraea (Euphorbiaceae). Syst. Bot. 9: 458-466.

Hayden, W. J. 1986. Floral morphology and relationships of Neowawraea (Euphorbiaceae). Virginia Academy of Science Meeting, Harrisonburg, Virginia. ABSTRACT: Virginia J. Sci. 37: 78.

Hayden, W. J. 1987. The identity of the genus Neowawraea Rock (Euphorbiaceae). A.I.B.S. Annual Meeting, Columbus, Ohio. ABSTRACT: Amer. J. Bot. 74: 736.

Hayden, W. J. 1987. The identity of the genus Neowawraea (Euphorbiaceae). Brittonia 39: 268-277.

Hayden, W. J. 1990. Flueggea Willd. Pp. 620-621. In: W. L. Wagner, S. H. Sohmer & D. Herbst, Manual of the Flowering Plants of Hawai'i. University of Hawaii Press and Bishop Museum Press, Honolulu.

Opportunities for student projects with Flueggea (Neowawraea) - 1. Establishment of Flueggea neowawraea germplasm in cultivation (will be absolutely dependent upon securing co-operation and guidance from botanists in Hawaii. 2. Survey of leaf anatomy in the genus Flueggea with a focus on the interplay of ecological/environmental adaptations and relationships.

Chamaesyce - In the course of my work with various euphorbiaceous plants I eventually became acquainted with the genus Chamaesyce, a distinctive group of weedy, C4 photosynthesizers postulated long ago to be derived from species of Euphorbia via a straightforward reduction process so that the whole plant body in Chamaesyce could be interpreted to be homologous with the reproductive portion (pleiochasium) of species in Euphorbia subgenus Esula or subgenus Agaloma. With funding from the Jeffress Trust, I undertook a comparative and developmental study of the key structures putatively thought to be homologous, the plexus of branches that forms at ground level in Chamaesyce and the whorl of branches that signal the transition to the flowering phase in species of Euphorbia. In short, the two regions are developmentally and anatomically dissimilar and, thus, the long-held putative homology is not supported by anatomical evidence. To date, published materials document this conclusion for Chamaesyce maculata, a typical prostrate species, and several species with erect growth habits (C. hirta, C. hypericifolia, and C. mesembrianthemifolia). The latter study included SEM images of critical developmental stages and included much work done by an undergraduate student (see citations, below).

In the course of germinating seeds of Chamaesyce maculata I observed the rapid formation of a mucilage layer on the seed coat in response to water. I had never heard of a thing at the time, and was quite chagrined when, a few months later, a paper appeared describing the cells and structures involved in exactly the same species formidable detail. But I had also observed that another species, C. mesembrianthemifolia, failed to form mucilage, even after prolonged exposure to water. I also knew that these two species were classified in different sections of the genus Chamaesyce, so with the help of an undergraduate student (see citations below) we undertook a survey of mucilaginous testa throughout the genus, and found its occurrence to be reasonably well-correlated with the major taxonomic divisions of Chamaesyce. Further, via SEM, we were able to correlate mucilage production with other structural details of the testa.

Another student (see citations) completed a systematic revision of a group of Chamaesyce species known as the "Pleiadenieae" for his honors thesis. This group was of critical interest because of their supposed intermediate position between Euphorbia and the rest of the genus Chamaesyce. These plants had not received comprehensive critical study since the 1860s and 1870s.

Rosengarten, M., & W. J. Hayden. 1983. Stem ontogeny in Chamaesyce hirta (Euphorbiaceae). Virginia Academy of Science Annual Meeting Fairfax, Virginia. ABSTRACT: Virginia J. Sci. 34: 142.

Hayden, W. J. 1985. Stem ontogeny and phylogeny in Chamaesyce. Virginia Academy of Science Meeting, Williamsburg, Virginia. ABSTRACT: Virginia J. Sci. 36: 119.

Hayden, W. J. 1988. Ontogeny of the cotyledonary region of Chamaesyce maculata (Euphorbiaceae). A.I.B.S. Annual Meeting, Davis, Calif. ABSTRACT: Amer. J. Bot. 75(no. 6, pt. 2): 178.

Hayden, W. J. 1988. Ontogeny of the cotyledonary region of Chamaesyce maculata (Euphorbiaceae). Amer. J. Bot. 75: 1701-1713.

McGuire, W. & W. J. Hayden. 1990. Anatomical comparison of woody tissues of Chamaesyce nutans and C. hypericifolia (Euphorbiaceae). Virginia Academy of Science Meeting, Fairfax, Virginia. ABSTRACT: Virginia J. Sci. 41: 67.

Jordan, M. S., & W. J. Hayden. 1992. Anatomy of the seed surface in Chamaesyce: preliminary studies of the mucilaginous layer. Virginia Academy of Science Meeting, Richmond, Virginia. ABSTRACT: Virginia J. Sci. 43: 238.

Jordan, M. S., & W. J. Hayden. 1992. A survey of mucilaginous testa in Chamaesyce. Collect. Bot. (Barcelona) 21: 79-89.

Simmons, M. P., & W. J. Hayden. 1994. Systematics of Chamaesyce subsection Pleiadeniae (Euphorbiaceae). Virginia Academy of Science Meeting, James Madison University, Harrisonburg, Virginia. ABSTRACT: Virginia J. Sci. 45: 72.

Hayden, W. J. & O. G. Troyanskaya. 1997. Seedling development in two species of Chamaesyce with erect growth habits. Virginia Academy of Science Meeting, Virginia Tech, Blacksburg, VA. ABSTRACT: Virginia J. Sci. 48:96.

Simmons, M. P., & W. J. Hayden. 1997. Revision of the cerrado hemicryptophyte Chamaesyce of Boissier's "Pleiadeniae" (Euphorbiaceae). Brittonia. 49: 155--180.

Hayden, W. J. & O. Troyanskaya. 1998. Seedling development in species of Chamaesyce with erect growth habits. Sida 18: 43--55.

Opportunities for student projects with Chamaesyce - Assistance is needed for studies of seedling ontogeny in species of the "Pleiadeniae" group (native to southern Brazil and adjacent regions), the Acutae group (native to Texas and adjacent Mexico), and certain Hawaiian species; acquisition of suitable specimens is a pre-requisite for making progress with any of these potential projects.

Floristic inventories - Although the plants of Virginia are reasonably well known, in general, our knowledge of the geographic distribution of plants (exactly which plants occur in what parts of the state) is still somewhat sketchy. This knowledge is obtained by the collection and curation of herbarium specimens, the raw data of systematics and biogeography. Some parts of the state have been well-collected while others are much less well known. Further, comprehensive collecting projects are excellent means for students to become knowledgeable about local plant diversity, and the collections produced, when added to an herbarium, become useful materials for teaching and research. Below are citations related to two floristic inventories that I and my students have pursued to closure.

Hayden, W. J., & M. F. Johnson. 1986. Flora of Richmond National Battlefield Park (Chickahominy Bluffs, Cold Harbor, Fort Darling, Fort Harrison, Garthright House, and Watt House units). U.S. Department of the Interior, National Park Service, Research/Resources Management Report MAR-16, 40 pp.

Hayden, W. J., M. L. Haskins, & M. F. Johnson. 1988. Flora of Richmond National Battlefield Park (Beaver Dam Creek, Malvern Hill, and Parker's Battery units). U.S. Department of the Interior, National Park Service, Research/Resources Management Report, MAR-27, 33 pp.

Hayden, W. J., M. L. Haskins, M. F. Johnson, & J. M. Gardner. 1988. Flora of Richmond National Battlefield Park, Virginia. Virginia Academy of Science Meeting, Charlottesville, Virginia. ABSTRACT: Virginia J. Sci. 39: 126.

Hayden, W. J., M. L. Haskins, M. F. Johnson, & J. M. Gardner. 1989. Flora of Richmond National Battlefield Park, Virginia. Castanea 54: 87-104.

Simmons, M. P., D. M. E. Ware, & W. J. Hayden. 1993. The vascular flora of the Potomac River drainage of King George County, Virginia. Virginia Academy of Science Meeting, Old Dominion University, Norfolk, Virginia. ABSTRACT: Virginia J. Sci. 44: 123.

Simmons, M. P., D. M. E. Ware, & W. J. Hayden. 1995. The vascular flora of the Potomac River watershed of King George County, Virginia. Castanea 60: 179--209.

Opportunities for student projects with floristic inventories - Almost unlimited; any reasonable sized area with natural vegetation may prove of interest.

Penthorum - My first graduate student (see citations, below) wanted to work on a wetland plant from Virginia and Penthorum seemed to fit the bill. Penthorum sedoides--the "Ditch Stonecrop"--occurs along the margins of bodies of water throughout eastern North America. Another species, Penthorum chinensis, occurs in similar habitats in eastern Asia. The systematic placement of Penthorum was in doubt and there had been no thorough study of its anatomical structure, so my student's goal was to provide a thorough description of wood, node, and leaf of both species and assess what the anatomical evidence indicated in terms of relationships with Saxifragaceae and Crassulaceae, the two families thought to be most closely related. In general, she found that Penthorum lacked the distinctive synapomorphous features that might be used to define either Saxifragaceae or Crassulaceae. Thus, no compelling argument could be made to place it in either family, and we argued that the monotypic family Penthoraceae should be resurrected to accommodate this genus.

The gynoecium of Penthorum always seemed peculiar to me. Over a period of years in the 90's, I used Penthorum as the basis for several class projects, which led, eventually, to work by some additional undergraduate students on the anatomy and morphology of the gynmoecium of Penthorum. Contrary to the usual phyllosporous condition long-theorized to be the ancestral condition for flowering plants as a whole, we interpret the gynoecium of Penthorum to be stem-borne, or stachysporous. Moreover, preliminary studies reveal long-overlooked evidence for variability in carpel number in Penthroum sedoides.

Haskins, M. L., & W. J. Hayden. 1985. Anatomy and systematics of the ditch stonecrop, Penthorum. Virginia Academy of Science Meeting, Williamsburg, Virginia. ABSTRACT: Virginia J. Sci. 36: 119.

Haskins, M. L., & W. J. Hayden. 1985. Anatomy and systematics of Penthorum. A.I.B.S. Annual Meeting, Gainesville, Florida. ABSTRACT: Amer. J. Bot. 72(no. 6, pt. 2): 956.

Haskins, M. L., & W. J. Hayden. 1987. Anatomy and affinities of Penthorum. Amer. J. Bot. 74: 162-175.

Hayden, W. J. & J. D. Lewandowski. 1997. Gynoecium structure in Penthorum. Virginia Academy of Science Meeting, Virginia Tech, Blacksburg, VA. ABSTRACT: Virginia J. Sci. 48: 95.

Hayden, W. J. & J. D. Lewandowski. 1997. Anatomy and morphology of the gynoecium of Penthorum. A.I.B.S. Annual Meeting, Montreal, Canada. ABSTRACT: Amer. J. Bot. 84(6, Supplement): 201.

Opportunities for student projects with Penthorum - Assistance is needed in documentation of asynchrony in ovule development, and variability of carpel number.

Methyl salicylate roots of violets - My plant systematics class includes what I call "key-out guizzes," unknowns that the students must identify using the keys found in standard floristic works. During one spring semester in the late 1980s I happened to use a particular species of stemmed violet as an unknown. Most students were able to proceed accurately through the key to the violets, but, unexpectedly, many had trouble with the last few steps leading to the exact species at hand. It seems that the roots of the unknown specimen had a remarkably strong odor of oil of wintergreen, but this fact was indicated in the key only for a close relative. Many students reached the wrong identification because of this misleading shortcoming in the book. But, as the saying goes, there are no problems, only opportunities. As the class and I sorted through the confusion, it seemed likely that several closely related violets in subgenus Melanium all have wintergreen-like contents in their roots. One particularly enthusiastic student from that class (see citations, below) decided to straighten things out, at least for the species readily available in Virginia. With help from a colleague in the Department of Chemistry, we determined that the compound was indeed oil of wintergreen (methyl salicylate), that it is found in both Viola arvensis and V. rafinesquii, and that the compound occurs in specialized secretory cells located in the endodermis layer of the root.

Hayden, W. J., & J. Clough. 1989. Identification and localization of methyl salicylate in roots of Viola subgenus Melanium. Virginia Academy of Science Meeting, Richmond, Virginia. ABSTRACT: Virginia J. Sci. 40: 63.

Hayden, W. J., & J. Clough. 1990. Methyl salicylate secretory cells in roots of Viola arvensis and V. rafinesquii (Violaceae). Castanea 55: 65-70.

Amanoa - While sectioning leaves of various phyllanthoids in graduate school, I happened across the remarkable sclereid-containing epidermal cells of Amanoa. The student who initially worked on Neowawraea (above) also initiated an anatomical survey of the leaves of Amanoa, working with leaf fragments generously provided by the Smithsonian Institution. From what we know now, it appears that each species in the genus has its own distinct structural pattern of sclerified cells. But initial results from the student's anatomical studies were murkey and we gradually realized that the problem stemmed from a number of gross mis-identification of specimens in the collections of the Smithsonian Institution. At which point, I resolved to undertake a thorough study of the genus, encompassing all available collections from North American, South American, and European herbaria. My work has progressed to the point recognizing and naming several new species, an account of the genus for the "Flora of the Venezuelan Guyana," a published study of wood anatomy in the genus, a draft of a detailed monograph of the genus and drafts of floristic treatments of the genus for Colombia and the Guianas. The original sclereid study remains unpublished and awaits the inclusion of SEM images.

Hayden, W. J. 1990. Notes on neotropical Amanoa (Euphorbiaceae). Brittonia 42: 260-270.

Hayden, W. J. 1991. Taxonomic studies of Amanoa (Euphorbiaceae). Virginia Academy of Science Meeting, Blacksburg, Virginia. ABSTRACT: Virginia J. Sci. 42: 183.

Hayden, W. J., M. P. Simmons, & L. Swanson. 1993. Wood anatomy of Amanoa (Euphorbiaceae). IAWA Jour. 14: 1-9.

Hayden, W. J. 1999. Amanoa (Euphorbiaceae). Pp. 95–99, in: J. A. Steyermark et al., eds., Flora of the Venezuelan Guayana, Missouri Botanical Garden Press.

Opportunities for student projects with Amanoa - Assistance is needed with SEM studies of leaf features, producing publishable distribution maps for all species, and cladistic analyses of species within the genus.

Tetracoccus - Tetracoccus is a small genus of desert shrubs found in southern California, Arizona, and Mexico. It is the only member of Euphorbiaceae subfamily Oldfieldioideae found in the US. Thus, I was pleased to volunteer to produce a treatment for Tetracoccus for the Flora North America project and for the Vascular Plants of Arizona project.

Hayden, W. J. 1996. The genus Tetracoccus in North America. Virginia Academy of Science Meeting, Virginia Commonwealth University, Richmond, Virginia. ABSTRACT: Virginia J. Sci. 47: 102.

Hayden, W. J. (in press). Tetracoccus. In: L. Landrum, C. Mason, D. Pinkava, J. Reeder, and R. Van Devender, eds., Vascular Plants of Arizona.

Hayden, W. J. (in press). Tetracoccus Parry. In: Flora North America Editorial Committee (eds), Flora of North America. Oxford University Press.

Croton - Stems of Croton, one of the largest and most diverse genera in Euphorbiaceae, are characterized by several unusual anatomical features derived from bicollateral bundles with the potential to form two distinct cambia, the innermost of which can result in the formation of medullary bundles. Aside from a single survey published over a century ago, and work from our lab, virtually no other reports of these unusual features exist.

Hayden, S. M., & W. J. Hayden. 1993. Stem anatomy and medullary bundles of Croton glandulosus var. septentrionalis (Euphorbiaceae). Virginia Academy of Science Meeting, Old Dominion University, Norfolk, Virginia. ABSTRACT: Virginia J. Sci. 44: 119.

Hayden, S. M., & W. J. Hayden. 1994. Stem development, medullary bundles, and wood anatomy of Croton glandulosus var. septentrionalis (Euphorbiaceae). IAWA Jour. 15: 51-63.

Discocarpus - Interest in this small genus from Amazonia stemmed from the fact that it and Amanoa appear to be the only genera in Euphorbiaceae subfamily Phyllanthoideae with sclereids in foliar epidermis. Graduate student Sheila Hayden did a revision of the genus, including naming one new species. She also did a comparative study of leaf anatomy for the three species she recognized in the genus.

Hayden, S. M., & W. J. Hayden. 1996. A revision of Discocarpus (Euphorbiaceae). Ann. Missouri Bot. Gard. 83: 153--167.

Saururus - Saururus cernuus is a wetland plant found throughout eastern North America. It is known as Lizard's Tail, for its distinctive recurved inflorescence. Whereas all previous literature had suggested that rhizomes and stems of Saururus possess only primary growth, a recently published study of the anatomy of Saururaceae interpreted the bundles to contain secondary xylem. To help resolve the apparent discrepancy between the older and more recent literature, an undergraduate student (see citation, below) undertook a developmental study to document the progressive accumulation of xylem elements from rhizome tips to mature regions several years old. Whereas locally collected Virginia material show scant evidence of secondary xylem, a sample from Louisiana was reasonably consistent with Carlquist's report.

Hayden, W. J. & L. S. Machut. 1997. Does the rhizome of Saururus cernuus undergo secondary growth? Virginia Academy of Science Meeting, Virginia Tech, Blacksburg, VA. ABSTRACT: Virginia J. Sci. 48: 96.

Machut, L. S. & W. J. Hayden. 1998. Further studies of xylem development in the rhizomes of Saururus cernuus. Virginia Academy of Science Meeting, George Mason University, Fairfax, VA. ABSTRACT: Virginia J. Sci. 49: 70.

Opportunities for student projects with Saururus - More studies focusing on geographic and edaphic influences on secondary xylem formation in the rhizomes are needed.

Chonocentrum - While working on Discocarpus, attention was focused on this poorly known genus from the upper Rio Negro region of Brazil. To the best of our knowledge, Chonocentrum was collected only once, in the 1850s. There are no published illustrations of this plant, and we believe that it has been mis-placed taxonomically.

Hayden, W. J., & S. M. Hayden. 1996. Two enigmatic biovulate Euphorbiaceae from the neotropics: relationships of Chonocentrum and the identity of Phyllanoa. A.I.B.S. Annual Meeting, Seattle, Washington. ABSTRACT: Amer. J. Bot. 83(6-supplement): 162.

Phyllanoa - Studies of Chonocentrum brought to light problems with Phyllanoa. This genus from moderately high altitude in the Colombian Andes is also known from a single collection. It has been referred to Euphorbiaceae tribe Antidesmeae (subfamily Phyllanthoideae), however, we feel that the plant really belongs in Violaceae.

Hayden, W. J., & S. M. Hayden. 1996. Two enigmatic biovulate Euphorbiaceae from the neotropics: relationships of Chonocentrum and the identity of Phyllanoa. A.I.B.S. Annual Meeting, Seattle, Washington. ABSTRACT: Amer. J. Bot. 83(6-supplement): 162.

Hayden, W. J., & S. M. Hayden. 2000. Relationships of Chonocentrum (Euphorbiaceae). Virginia Academy of Science Meeting, Radford University, Radford, VA. ABSTRACT: Virginia J. Sci. 51: 95.

Acalyphoideae - wood anatomy - At a conference on Euphorbiaceae held at the Missouri Botanical Garden in the early 1990s, subfamily Acalyphoideae was referred to repeatedly as "the heart of darkness of Euphorbiaceae," a reference to the need for comparative data to help sort out relationships among this large and poorly known group of plants. So when I received an invitation to present a paper at a session on wood anatomy at the 1999 International Botanical Congress, Acalyphoideae seemed like it would prove a worthy topic. Despite the discovery of several genera with anatomically distinct wood structure (laticifers in Dicoelia and one species of Dalechampia, thick-walled fibers and scalariform perforations in tribe Galeariae, etc.) most acalyphoid woods were too uniform to reveal systematically useful characters. The black and white SEM images (19, 20, and 21) depict perforated ray cells with various forms of perforation plates.

Hayden, W. J., & S. M. Hayden. 1999. Wood anatomy of Acalyphoideae (Euphorbiaceae). Paper presented at XVI International Botanical Congress. ABSTRACT: IAWA Journal 20: 108-109.

Hayden, W. J., & S. M. Hayden. 2000. Wood anatomy of Acalyphoideae (Euphorbiaceae). IAWA Journal 21: 213–235.

Acalypha deamii - This little plant (above, center) was thought to be restricted to flood plain habitats within the Ohio River drainage basin. However, quite by accident, I discovered a population at the Huguenot Woods area of James River Park, just a stone's throw from UR. Several seasons of field work have now shown Acalypha deamii to be present on the James, Rappahanock, Shenandoah, and Potomac Rivers. Reproductive structures for related species of Acalypha are also shown above, left, A. gracilens, right, A. rhomboidea.

Hayden, W. J. & S. M. Hayden. 1998. Anatomy of secondary xylem in the Acalypha virginica complex. Virginia Academy of Science Meeting, George Mason University, Fairfax, VA. ABSTRACT: Virginia J. Sci. 49: 70.

Opportunities for student projects with Acalypha - Developmental studies of "normal" reproductive structures in the Acalypha virginica complex, for comparison with the allomorphic pistillate flowers and fruits of Acalypha deamii.

Floristics of Yucatan, Mexico - This work has had two focal points. First, since 2000, I have worked to document plant diversity of the forest at Kaxil Kiuic (The Helen Moyers BioCultural Reserve), located in the southern Puuc Region of the state of Yucatan, Mexico. As of summer 2006, approximately 450 species. have been documented via herbarium specimens (deposited at URV, UADY, and CICY) and digital photographs which can be viewed at my Flora of Kaxil Kiuic web site. Also I am pursuing the floristics of various members of the plant family Euphorbiaceae as they occur throughout the Yucatan Peninsula.

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