Showing papers in "Systematic Botany in 1979"

Distribution of Pollen Types in Vernonia (Vernonieae: Compositae)

Abstract: Vernonia is the largest genus of the tribe Vernonieae with nearly 1000 species found predominately in the New and Old World tropics. Morphological variation in vegetative features is extensive; however, floral characters are relatively uniform. This uniformity has led to difficulties in understanding relationships within Vernonia. Pollen morphology is distinctive however, and of taxonomic value in as- sessing infrageneric groups. In an attempt to understand better the patterns of radiation in the genus, pollen from over 500 species of Vernonia was examined from throughout the geographical range by light microscopy and SEM. There are six basic types of pollen grains. The distribution of pollen types is correlated with the radiation of related species groups. A widespread, probably ancestral, pollen type is found in both the New and Old Worlds, but other types are found to be exclusive to, or to predominate in, one hemisphere. Structural changes appear to be associated with functional modifications. The pattern of pollen distribution appears to reflect the evolutionary divergence of species within the genus over time and supports a broad concept of the genus.

Factors Determining Fruit Set in Heterostylous Bluets, Houstonia caerulea (Rubiaceae)

Abstract: Subpopulations of heterostylous Houstonia caerulea consist of both pin and thrum plants (heterogeneous) or of plants of a single morph (homogeneous). Crossing experiments demonstrate that pollination between morphs is essential for maximal fruit set. In heterogeneous subpopulations percent fruit set increases as the ratio of pins to thrums approaches unity. Fruit set also is positively correlated with subpopulation size but shows little relationship with distance to the nearest compatible subpopulation. In homogeneous subpopulations, however, fruit set decreases with increasing subpopulation size, and distance to the nearest compatible subpopulation is more important in determining percent fruit set. Substructuring, therefore, may profoundly affect the reproductive biology of plant populations. Heterostylous plants present population biologists with a unique tool for examining problems concerned with plant reproductive biology and spatial patterns in natural populations. Individuals of such species can easily be segregated morphologically into two genetic incompatibility groups. In Houstonia caerulea members of the long-styled group, commonly known as "pins," have anthers attached low in the corolla tube, small pollen grains, and large stigmatic papillae (Rothrock, 1868; Darwin, 1877; Meehan, 1880; Lewis, 1962, 1976; Ornduff, 1977). "Thrums" have short styles, anthers attached high in the corolla tube, large pollen grains, and small stigmatic papillae. Thrums usually represent the "Ss" heterozygote and pins, the "ss" homozygote, in terms of the genetics of the incompatibility system (Vuilleumier, 1967; Yeo, 1975). Such a system of enforced outcrossing should maintain an equal ratio of pins to thrums. The comparative ease in working witha visible genetic polymorphism such as heterostyly has allowed researchers to gather much information on disassortative pollination and pollination efficiencies in natural systems (Levin, 1968; Mulcahy & Caporello, 1970; Ornduff, 1970a, 1970b, 1971, 1975a, 1975b, 1976; Ganders, 1974, 1975a, 1975b, 1976; Dulberger, 1975). It also has made possible the demonstration of spatial patterning in plant populations (e.g., Levin, 1974; Ornduff & Weller, 1975). One question which has not been approached in heterostylous plants however, is the identification and quantification of extrinsic factors determining levels of fruit set. In non-heterostylous plant populations such factors as plant spacing (Levin & Kerster, 1968; Levin, 1972), plant density (Levin & Kerster, 1969a, 1969b), inflorescence size and form (Willson & Rathcke, 1974; Willson & Price, 1977; Wyatt, 1978, 1980) and ' Botany, Duke University, Durham, NC 27706; Present address of RW: Botany, University of Georgia, Athens, GA 30602.

A Light and Scanning Electron Microscope Study of Seed Morphology in Agalinis (Scrophulariaceae) and its Taxonomic Significance

Abstract: Seeds of 33 species of Agalinis were examined with the scanning electron microscope and the light microscope. Thin sections were cut of resin-embedded seeds from 11 taxa. The outer cells of the seed coats of all taxa form a reticulum. Thickenings (lignifications) are present on the inner tangential walls of cells making up the reticulum. The radial walls of the outermost cells of the seed coat and the thickenings on the inner tangential walls of these cells are smooth or variously or- namented. The seeds of Agalinis are classified into five major types based on seed shape, size, and color; cell shape and ornamentation; and pattern and ornamentation of thickenings. Species in certain previously recognized sections and subsections of the genus have seeds of a single type. In other cases the occurrence of species with dissimilar seeds within a section or subsection adds support to other morphological evidence that indicates a reclassification is warranted. While many species have char- acteristic seed patterns, infraspecific taxa cannot be differentiated on the basis of

An Outline of the Systematics of Oenothera subsect. Euoenothera (Onagraceae)

Abstract: A new taxonomy is proposed for Oenothera subsect. Euoenothera (Ona- graceae). In this group, the species that are homozygous for the three major genomic complexes, A, B, and C, are well separated from one another. Within each of these three complexes, species that form bivalents or relatively small rings of chromosomes are represented: AA (0. elata, 0. Iongissima, 0. jamesii), BB (0. grand flora), and CC (0. argillicola). There are also complex heterozygotes with the AA (0. villosa, 0. woifil) and BB (0. austromontana) genomic constitutions. The entity that has been called 0. hookeri subsp. wolfii is an AA complex heterozygote, probably of separate origin from 0. villosa and here accorded taxonomic recognition as a species, as is the BB homozygote hitherto called 0. biennis subsp. austromontana. Each of the three possible combinations between the A, B, and C genomes is also recognized taxo- nomically: AB (0. biennis), AC (0. oakesiana, earlier considered a subspecies of 0. parv flora), and BC (0. parviflora). Oenothera glazioviana (0. lamarckiana auct., 0. erythrosepala) has the constitution AB, like 0. biennis, and may have originated fol- lowing hybridization between 0. biennis or 0. grand flora as the pistillate parent and 0. elata (0. hookeri) as the staminate parent: this probably occurred in a garden in Europe. Minor forms, many of hybrid origin, that have originated in Europe are relegated to the species they resemble most closely. To recapitulate the taxonomic changes with respect to the most recent North American taxonomic treatment (Munz, 1965), the complex heterozygote 0. wololi (AA) is separated as a species from the bivalent-forming 0. elata; 0. austromontana (BB) is separated as a species from 0. biennis (AB); and 0. parviflora (BC; = Parviflora-1) is separated from 0. oakesiana (AC; = Parviflora-2). The races that have been called Biennis-1, in which the B-complex is transmitted through the egg, and Biennis-2, in which the A-complex is transmitted through the egg, are not separated taxonomically, not usually being distinguishable in nature, despite the subspecific recognition accorded them by Munz. Among the non-com- plex-heterozygotes, 0. hookeri is regarded as a synonym of 0. elata, because of the limited distinctiveness of these two entities as recognized earlier, and their broad geographical intergradation. Oenothera glazioviana (1882) is an earlier name for what has recently been called 0. erythrosepala (1903), and, prior to that, 0. lamarckiana by de Vries. Earlier attempts to create a taxonomy for this subsection, particularly in recent years in Europe, have split the species too finely for a general purpose tax- onomy, mainly in imitation of genetic analyses but without the requisite genetic information in most cases to do this consistently.

Variation in Heterostylous Reproductive Systems Among Populations of Oxalis alpina in Southeastern Arizona

Abstract: Numerous stages in the evolution of distyly from tristyly may be ob- served among populations of Oxalis alpina in southeastern Arizona. At one extreme, the mid form is common in populations and features of floral morphology are similar to those of typical trimorphic species. At the other extreme, the mid form is absent and few of the morphological features of tristyly have been retained. A spectrum of populations with intermediate mid frequencies and floral morphology connects these extremes. Modifications of style form representation and floral mor- phology are consistent with those expected in populations where modified incom- patibility has resulted in selection against the mid form. Disjunction of populations and variation in evolutionary rates have probably resulted in the diversity of inter- mediate reproductive systems occurring in this region.

Allozyme variation and evolution in Solanum section Androceras.

Abstract: Four populations of two climax perennial species and 19 populations of eight colonizing annual species of section Androceras were surveyed for allozyme variation controlled by seven genes. Most populations of the annuals were mono- morphic at all seven loci. Populations of perennials were substantially more variable. It is postulated that genetic bottlenecks associated with colonization may explain the low levels of variability encountered in annual populations. Speciation in section Androceras seems to be universally accompanied by evolution of internal barriers to hybridization that cause hybrid seeds to abort. The strength of these barriers is correlated with interpopulation genetic distance, suggesting that they arise as inci- dental by-products of divergent evolution. Interspecific genetic distances in section Androceras do not indicate an unusually rapid rate of speciation, and taxonomic species diversity in Solanum may instead reflect great age of the genus. A biochemical similarity dendrogram based on genetic distance is in overall agreement with esti- mates of phylogeny in section Androceras based on other criteria, but several taxa seem to be misplaced. Effects on genetic distance of natural hybridization and vari- ance associated with the small sample of genes may be responsible for errors in phylogenetic interpretation. Section Androceras (Nutt.) Bitt. ex Marzell includes 12 of the ca. 2000 species in Solanum. The section has recently been a subject of intensive systematic investigation, leading off a projected series of studies on tax- onomy and evolution in sections of the prickly subgenus Leptostemonum

The genus Glandularia (Verbenaceae) in North America

Abstract: -The genus Glandularia is recognized as a valid genus distinct from Verbena based on consistent differences in seed morphology, chromosome number, the length of the style, reproductive modes, ploidal levels, and continent of origin. Eight new chromosome counts are given. Also a revision of the taxonomy of the 23 North American species of Glandularia is presented. Two sections, three new species, and one new variety are recognized. In his 13th edition of Linneaus' "Systema," Gmelin (1791) established the genus Glandularia with a single species, Glandularia carolinensis based on Walter's Anonymous caroliniensis (1788). From Gmelin's original description, borrowed from Walter, Germen 4 partitum. Stil. 2fidus, glandula inter utramque laciniam media, it seems quite reasonable to assume that the name Glandularia was derived from the glandular appearance of the stigmatic area rather than the glandular hairs of the calyx and floral bract or the glandular appendage on the anther connective as might be supposed. A New World genus of annual or perennial herbs, Glandularia, grows in habitats ranging from the margins of mesic woodlands to dry desert slopes. Species of Glandularia usually grow in an open, often disturbed habitat. Although they can be found in flower during all months of warm weather, they flower primarily in the spring and again in late summer and fall. Glandularia has a disjunct distribution in North and South America. In North America it can be found from Guatemala to South Dakota and from Virginia and Florida to Arizona. South American species are known from Peru, Chile, Uruguay, Bolivia, Paraguay, Argentina, and southern Brazil. Although no complete taxonomic treatment is available for the South American species, there are probably more than fifty. The North American species were monographed by Perry (1933) who recognized 19 species, 6 varieties, and one form under Verbena section Glandularia Schauer. In North America Glandularia grows from Guatemala to South Dakota and from Virginia and Florida to California. The greatest diversity is found in the southwestern United States and in northern Mexico. The taxonomic status of the genus Glandularia has been perceived differently by a number of different authors. The taxa placed here in the genus Glandularia have been given sectional rank under Verbena (Perry, 1933), subgeneric rank under Verbena (Lewis & Oliver, 1961), or generic rank (Schnack, 1944, 1964; Schnack & Covas, 1944, 1946; Small, 1933) based on morpholoXical, anatomical, and cvtological eviI Botany, University of Wyoming, Laramie, WY 82071.

A Study of Wild Leek, and the Recognition of Allium burdickii (Liliaceae)

Abstract: The combination of reproductive isolation and significant morpholog- ical differences supports the recognition of two species of wild leek: Allium tricoccum Solander in Aiton and A. burdickii based on A. tricoccum var. burdickii Hanes. Plants of the latter are considerably smaller and have fewer flowers per umbel than those of the former. They also consistently lack the red pigmentation usually evident in scapes and petioles of A. tricoccum. Although the two taxa often occur together, hybridization between them is precluded by a phenological barrier. In 1977 and 1978, Illinois populations of A. burdickii flowered from June 2-21, while those of A. tricoccum began flowering about July 1. An estimated frequency of occurrence based on herbarium collections indicates that the probable center of distribution for A. burdickia lies in the area bounded by northern Illinois, northern Indiana, southern Wisconsin and southern Michigan. In the eastern United States, A. tricoccum seems to be the more common of the two species. As no type specimen of A. tricoccum can be found, a neotype is designated. Allium tricoccum Solander in Aiton (1789) is the eastern North Amer- ican counterpart of the Old World ramson or bear leek, A. ursinum Lin- naeus. Known in the Midwest as wild leek and in the Appalachian Moun- tains as ramps, the species is a forest floor component of the northern hardwood association. The plants do not occur west of the 100th merid- ian. In the Great Lakes area and northeastward, they grow on streamside bluffs, in depressions, and in maple-dominated upland woods. In the southern extension of range, the plants are confined to colluvial moun- tain slopes at increased elevations (between 1000 and 3000 m), probably as a response to the higher prevailing temperatures. The existence of two well-defined morphological variants of wild leek was first reported by Hanes and Ownbey (1946) who studied populations in the woodlands of Prairie Ronde Township, Kalamazoo County, Mich- igan. They published and elaborated short descriptions taken from a letter by J. H. Burdick to Asa Gray which had accompanied specimens collected in 1877 in Milton, Wisconsin. Gray, and subsequently Fernald, considered the variations a response to environmental factors and, re- portedly with some reluctance, Hanes and Ownbey adopted the concept of "ecological races" for the two taxa. In addition to the morphological distinction based primarily on differences in size and type of pigmen- tation, the authors also noted differences in the floral development of the two taxa. In 1953 Hanes published the name Allium tricoccum var. burdickii in honor of the man who first noticed and collected this variant. No type or authentic specimen could be found for Allium tricoccum.

A systematic histological of palm fruits. II. The Areca alliance.

Abstract: Pericarp structure in the ten genera of the Areca alliance is more het- erogeneous than in the Ptychosperma alliance, but with some species closely approach- ing the ptychospermate condition The endocarp is generally less well-defined, al- though composed of the same tissue types Fibrovascular bundles functioning as part of the endocarp tend to be more dispersed among mesocarp tissues, sclerified ground tissue is less prominent, but the locular epidermis shows about the same range of variation Four different types of exocarp are found in the group: 1) a layer of brachysclereids; 2) a layer of brachysclereids plus fibrous bundles; 3) a series of fibrous bundles alone; 4) a dense layer of specialized tanniniferous cells Fibrous bundles can occur among the vascular bundles, or as separate series in the middle or outer pericarp The alliance appears to be taxonomically divisible into two groups, on the basis of presence or absence of brachysclereids in the exocarp Other minor taxonomic suggestions are made In this paper, the pericarp histology of representatives from the ten genera of the Areca alliance (sensu Moore, 1973) is described This is the second in a series of papers, of which the first dealt with the Ptychosperma alliance (Essig, 1977) The aim of these investigations is to provide a broad survey of the family, in a taxonomic framework, including, where possible, at least one representative from each genus in the family Such a survey is necessarily shallow, especially where a large genus is repre- sented by only one or a few species This survey will, however, provide the "first look" at fruit structure in many genera, will provide a uniform terminology for describing fruit structures in the palm family, will char- acterize the general fruit structure of the alliances and of some small genera, and will suggest characters of potential diagnostic value to be investigated in more detailed studies of larger genera The Areca alliance is one of the more advanced in the family by the criteria of Moore (1973), and is broadly distributed in the Old World tropics, from India to Micronesia and the New Hebrides The ten genera together contain about 270 species The largest is Pinanga, with 120 species, but several genera contain only one or a few species (Loxococcus, Gigliolia, Nenga, and Siphokentia) Fruits are generally similar to those of the Ptychosperma alliance, with usually pseudomonomerous gynoecia re- sulting in single-seeded drupes with apical stigmatic residues

Serological Investigation of Selected Amentiferous Taxa

Abstract: Quantitative and qualitative analyses for serological affinities within and among taxa of selected families of the "Amentiferae" were employed in this research. With only a few exceptions, there was good agreement between protein similarity as measured by the Boyden procedure, and the number of immunoprecipitating systems remaining after presaturation of the experimental sera. The Myricaceae, Juglandaceae, and Fagaceae revealed a degree of serological correspondence sufficient to warrant retaining them in the subclass Hamamelidae. The low levels of serological correspondence among taxa from these three families and the Anacardiaceae indicated a placement of the Anacardiaceae in a position divorced from the others tested. The obtained data provided support for Cronquist's and Takhtajan's classification of these taxa. In addition this investigation indicated that pollen, with its high protein content, provided an excellent source of extractable antigens for systematic serological research. The concept of a natural grouping of plants designated as the "Amentiferae" is no longer given serious credence, and many of the families included in this grouping have been dispersed in diverse orders (Stern, 1973). The present research includes a comparison of serological characteristics among genera of the following four families: (1) Juglandaceae-Carya, Juglans; (2) Myricaceae-Myrica, Comptonia; (3) FagaceaeQuercus, Fagus; (4) Anacardiaceae-Rhus, Toxicodendron. Table 1 presents a listing of some of the basic trends in the classification of these four families. The first major trend is that of Cronquist (1968, 1979), Takhtajan (1969), and Hutchinson (1959). These three considered the Fagaceae, Myricaceae, and Juglandaceae as being derived from hamamelidaceous stock, while the Anacardiaceae was considered tohave a rosidae or rutalian origin. By virtue of this juxtaposition, one might expect a greater degree of correspondence among the first three families than between them and the Anacardiaceae. A second trend is the grouping of the Juglandaceae, Myricaceae, and Anacardiaceae in the Rutalian complex and the Fagaceae in the Hamamelidian complex. This scheme, as espoused by Thorne (1968, 1976), placed the Anacardiaceae and the Juglandaceae in the order Rutales and the Myricaceae in the Myricales; whereas Dahlgren (1975) placed the three families, respectively, in the orders Sapindales, Juglandales, and the Myricales. Both classifications would postulate greater similarities among the Juglandaceae, Myricaceae, and Anacardiaceae, than between this grouping and the Fagaceae. However, in a publication by Gornall, Bohm 1 Botany, Rutgers University, New Brunswick, NJ 08903.

Pollen Dispersal in Natural Populations: A Method for Tracking Individual Pollen Grains

Abstract: Pollen dispersal studies in natural populations have been significantly hampered by the lack of a technique providing effective pollen labeling. Such a method has been developed which utilizes 14C labeling of pollen in the anther fol- lowed by identification of individual labeled grains using thick layer liquid emulsion autoradiography. This provides a safe, inexpensive and highly sensitive method of tracking individual pollen grains between plants or from plant to pollinator, etc., in natural populations. Pollen dispersal in natural populations is a poorly understood phe- nomenon in spite of its fundamental importance in the population bi- ology of plants. Four major types of techniques have been used to mea- sure pollen dispersal and all appear to have significant limitations as currently applied. One approach utilizes naturally occurring variation in pollen morphology to identify pollen. Sufficient natural variation in pol- len is uncommon within or between closely related species and relatively few studies have been able to use this straightforward approach. A sec- ond method of tracing pollen movement requires observation of pollen vectors (e.g., Levin et al., 1971). However, in many cases the vectors are

Dasysiphonia chejuensis gen. et sp. nov. (Rhodophyta, Dasyaceae) from Korea

Abstract: Dasysiphonia chejuensis gen. et sp. nov., a marine red alga belonging to the Dasyaceae, Ceramiales, is described from Cheju Island on the southern coast of Korea. The thallus grows sympodially, forming an indeterminate or determinate branch from every segment of main axes in bilateral-dorsiventral manner, and bears five pericentral cells derived alternately from each central cell. The main axes are lightly corticated. Spermatangial branches and tetrasporangial stichidia develop on monosiphonous determinate branches. Tetrasporangia are not completely protected by cover cells. Procarps bearing two sterile groups occur alternately in successive segments on specially developed polysiphonous fertile branchlets. The second or third pericentral cell adjacent to the first always becomes the supporting cell. The new genus morphologically resembles Heterosiphonia in its lateral-dorsiventral branch system, but is also similar to Dasya especially in tetrasporangium formation. At present the Dasyaceae (Ceramiales) is comprised of eleven genera which occur mainly in warm temperate marine regions, particularly Australia (Kylin, 1956; Parsons, 1975). Most genera are monotypic or consist of only a few species except for Dasya C. Agardh (perhaps 70 species), Dasyopsis Zanardini (about 10 species) and Heterosiphonia Montagne (about 40 species). In Korea only two species of Heterosiphonia and four species of Dasya are recorded from southern and eastern coasts affected by the Kuroshio current (Kang, 1966). From an island located on the southern coast of Korea (Fig. 1), we collected tetrasporic and procarpic plants of a red alga belonging to the Dasyaceae. They resembled Heterosiphonia in vegatative morphology, but appeared more related to Dasya in reproductive morphology. The vegetative and reproductive structures of these plants do not accord with any previously described genus. A new monotypic genus is therefore proposed to receive this new species. Dasysiphonia Lee and West, gen. nov. Frons erecta, sympodialis in incrementum, ramum indeterminatum vel determinatum ex omni segmento axium principalium in modo bilaterali et dorsiventrali formans, per hapteron rhizoideum affixa; axes principales corticantes laete polysiphonibus, 5 cellulas pericentrales e cellulis centralis alterne efficientes; rami indeterminati aliquot ordines ramorum lateralium in ordinatione eodem ac in axibus principalibus efferentes; rami determinati monosiphonibus I-vel 3-plo per incrementum sympodiale dividentes, in fila capilliformia in thallis veterioribus et ramulis femineis fertilibus transmutati; stichidia I Botany, University of California, Berkeley, CA 94720. Present address of IKL, Botany, Seoul National University, Seoul 151, Korea.

The Systematics of the Bidens ferulaefolia Complex (Compositae)

Abstract: Bidens ferulaefolia has been recognized as a species consisting of three varieties (var ferulaefolia, var foeniculifolia, and var ludens) widely distributed from southwestern United States through Mexico and into Guatemala Separation of these taxa was based on several highly variable morphological characters such as achene length, awn number, and degree of leaf dissection These taxa were studied utilizing field and herbarium material, morphological data, cytotaxonomic studies, green- house and hybridization experiments, and comparative flavonoid chemistry Results obtained from these investigations suggest that three species be recognized: B fer- ulaefolia, B carpodonta, and B longistyla Bidensferulaefolia occurs in disturbed habitats on the high plateau from Guanajuato in southcentral Mexico northwest into the foothills of the Sierra Madre Occidental in Chihuahua in northern Mexico Bidens carpodonta inhabits disturbed areas in mountain valleys or on high plateaus, while B longistyla is found in mountain valleys on gypsum and limestone outcrops, in the Sierra Madre Oriental of northeastern Mexico in the states of Nuevo Le6n and Coahuila Morphological characteristics based on quantitative and qualitative fea- tures, such as style branch lengths and presence or absence of a red pigment in the flowering heads, are useful for distinguishing the three taxa Cytotaxonomic data for these three species showed that B ferulaefolia has a chromosome number of n = 10, while B carpodonta and B longistyla are both n = 12 Hybridization experiments at the intra- and interspecific levels confirmed that each species is reproductively isolated from the other two Flavonoid comparisons of leaf and floral tissues from B ferulaefolia, B carpodonta and B longistyla established the presence of species- specific compounds that would allow for the chemical separation of these three taxa The two varieties previously recognized (var foeniculifolia and var ludens) are placed in synonymy with B ferulaefolia, whereas B carpodonta and B longistyla are distin- guished as species Finally, the geographical distribution formerly attributed to B ferulaefolia was examined and was found to involve a number of related species Throughout Mexico, particularly near the end of the rainy season in late September and October, one encounters population after population of grossly similar weedy Bidens annuals with large, yellow-rayed heads and pinnatisect leaves In his classical studies of the genus Bidens in 1937 and 1955, Sherff treated all such plants with square stems and dimorphic achenes as a single species, B ferulaefolia Three varieties were recog- nized in both taxonomic treatments Typical var ferulaefolia was by far the most common, occurring in Arizona southeastward into Mexico to the states of Jalisco and Puebla, and rarely into Guatemala This variety was characterized as having narrowly linear leaf segments and achenes which were 4-6 mm long with two aristae each The latter were report- edly "sometimes deciduous" In contrast, var foeniculifolia had leaves

Apportionment of Isozyme Variability in Polygonum pensylvanicum (Polygonaceae)

Abstract: The apportionment of genetic variability at ten isozyme loci was studied in six populations of Polygonum pensylvanicum L. Thirty percent of the isozymes are polymorphic and the average individual heterozygosity per plant is low, 4 percent. Populations are genetically similar; the mean standardized genetic variance among populations is 0.12. Most of the total genetic diversity, 87.3 percent, is due to dif- ferences between individuals within populations; 12.7 percent of the diversity results from differences between populations. None of the populations is in Hardy-Wein- berg equilibrium; deviation from equilibrium expectations is due to a deficiency of heterozygotes. The levels and apportionment of genetic variability within and among populations of plant species have been of major interest to plant evolu- tionists and systematists. A substantial body of theory predicts that levels of genetic variability will be related to numerous species characteristics such as karyotype, habitat, population structure, and generation length. The empirical evidence for these associations is still incomplete; the level and apportionment of genetic variability in many types of plant species is unknown. This study examines isozyme variability in a widespread weedy annual species, Polygonum pensylvanicum. Baker (1965) and others have predicted that annual weeds will have little genetic variation, both within and be- tween populations. Our purpose is to test these predictions by answering the following questions: 1) What is the level of genetic variability for the species? 2) How is the variability distributed within populations? 3) How genetically similar are populations? 4) How is the genetic diversity of the species apportioned? Polygonum pensylvanicum is a weedy herbaceous annual found in dis- turbed habitats, often near ponds or streams. The species is common from Minnesota east to New England, and Ohio north to Ontario. Plants may grow to a maximum of four feet in height, but are often much smaller in restricted environments. There may be from one to many flowering heads on a single plant and each infloresence is spikelike, hav- ing twenty to thirty perfect, self-fertile flowers. The flowers are insect pollinated, and in some populations, pollination by ants has been ob- served. One seed is produced per flower; seeds require a six month after- ripening period in a moist, 6?C environment before germination (Ran- son, 1935).

A Reevaluation of the Taxonomy of Salix tyrrellii, a Sand Dune Endemic

Abstract: Salix tyrrellii is an endemic taxon described from the active sand dunes south of Lake Athabasca, Saskatchewan. It is related to S. planifolia from which it differs in having slender erect branches which are often slightly tortuose, a pro- longed juvenile growth form, smaller and thicker leaves with stomata on both sur- faces and low concentrations of phenolic glycosides in bark tissues. Its amphisto- matous leaves link this taxon to some arctic populations of S. planifolia in the N.W.T. and Manitoba which may be ancestral to it. The growth form of S. tyrrellii is probably an adaptation to active sand dune habitats. Phenolic glycosides may play a role in its adaptation to active sand dunes. Because of its close relationship to S. planifolia, the new combination S. planifolia ssp. tyrreliji (Raup) Argus is proposed. An extensive system of active sand dunes lies along the south shore of Lake Athabasca in northwestern Saskatchewan and adjacent Alberta. Large dune fields covering 300 sq km and 30 sq km are located near the mouths of the William and MacFarlane Rivers, respectively. The region of actively blowing sand extends over 90 km along the lake shore and up to 20 km inland (Map 1). The dune fields consist of loose sand, some of which is blown into dunes up to 35 m tall, overlying gravel pavements and sandy glacio-fluvial materials. Smaller dunes scattered throughout the region are parabola dunes that have developed from blowouts in the sandy Pinus banksiana and Picea mariana forests that stabilize much of the sand area. The active sand habitat supports a distinctive flora made up of an unusually large number of endemic taxa together with disjunct arctic species and the more common boreal and northern Great Plains species.

Sphagnum subtile (Russow) Warnst. and Allied Species in North America

Abstract: Sphagnum subtile is recognized as a species occurring widely in north- eastern North America and occasionally in western North America in minerotrophic and often forested mires. By contrast, the allied species S. nemoreum and S. rubellum occur mostly in open, nearly ombrotrophic mires. A combination of non-falcate- secund branch leaves and triangular-lingulate to lingulate stem leaves with strong borders extending to the apex will separate S. subtile from S. nemoreum and S. ru- bellum. Sphagnum subtile (Russow) Warnst., frequently noted at the species (Isoviita, 1966; Malmer, 1966; Savich-Lyubovitskaya & Smirnova, 1968) or varietal level (Nyholm, 1969) in European treatments, has been vir- tually ignored by American bryologists. Andrews (1913) and Crum, Steere and Anderson (1973) have placed it in synonymy with S. capillaceum var. tenellum (Schimp.) Andr. (=S. rubellum Wils.). Warnstorf (191 1), how- ever, had noted it for the northeastern United States. Its acceptance even in Europe has been with some misgivings (Isoviita, 1966) and British workers have not considered it (Hill, 1978). As a result of my extensive observations of North American Sphagna, it became clear that S. subtile could be recognzied as a species closely allied morphologically but quite distinct ecologically and distributionally from S. rubellum and S. nemoreum Scop. (=S. capillifolium (Ehrh.) Hedw., S. capillaceum (Weiss) Schrank). In bryophytes, species distinctions are basically made on morphological bases but important additional information can also be gained from dis- tributional and ecological data, especially in Sphagnum, where data are more readily obtainable. Sphagnum subtile (Russow) Warnstorf 1903 Krypt. Brandenburg 1:

The Genus Crypsis (Gramineae) in the United States

Abstract: The Old World grass genus, Crypsis, is represented in the United States by three naturalized taxa. Although these are usually treated as specifically distinct in America, European botanists consider two of them to be merely different growth forms of the same species. The few chromosome counts in the literature suggest x = 9 as the basic number. Our studies, including chromosome counts from 44 popu- lations and seed protein analyses from 32 populations, demonstrate that the three taxa differ chemically and represent a polyploid series with a diploid, a tetraploid, and a hexaploid, and a basic chromosome number of x = 8. Each entity seems specifically distinct, and can be recognized by small, but consistent morphological characteristics. Evidence is presented indicating that the correct name for the species listed as C. niliaca in Hitchcock's Manual is Crypsis vagini/1ora (Forsk.) Opiz. Crypsis comprises seven or eight species of annual grasses native to the Old World, particularly the Mediterranean Region. These plants are characteristic of arid and semiarid habitats, especially those which are at least temporarily inundated during winter. Some workers have treated the genus as monotypic with a single species, C. aculeata (L.) Ait., the others being referred to Heleochloa Host ex Roemer. C. E. Hubbard (1947), in a lucid discussion of the Crypsis-Heleochloa problem, has point- ed out that all of the characteristics which have been employed to sep- arate the two genera are inadequate. These include (1) spikelets disar- ticulating above or below the glumes, (2) grain falling from the lemma and palea at maturity or remaining permanently enclosed between them, and (3) seed loose in the pericarp or adnate to it. He adds that even the one-nerved palea and two stamens of C. aculeata are not absolute, and cites collections of that species in which paleas with one or two nerves, and flowers with either two or three stamens occur. At present most agrostologists who have considered the problem treat Heleochloa as at most a subgenus. A few species of Crypsis have been introduced into the United States; the first collections have come from the east coast. There are also records of one species from several states bordering the Great Lakes. The only areas in which they have become established and are a significant part of the flora, however, appear to be the west, particularly California. One entity was erroneously identified as C. aculeata by Hitchcock (1912, 1920, 1935a, 1935b). In the second edition of Hitchcock's Manual (1951), how- ever, Agnes Chase took up the name C. niliaca Fig. & de Not. for these plants. The other two, C. alopecuroides (Pill. & Mitterp.) Schrad. and C.

Morphology, Anatomy, and Taxonomic Relationships of Otopappus australis (Asteraceae)

Abstract: A collection of Otopappus australis from Cerro Campana represents the first report for the genus from Panama. Aspects of the morphology at variance with the type description include longer and narrower leaves and narrower flowering heads. Details of stem and leaf anatomy are reported; exceptionally tall primary wood rays probably relate to the plant's vine-like habit. A variety of primitive and specialized features are found in the floral anatomy. Unusual topographic sites for trichomes include pappus awns, inside the corolla tube, anther appendages, and style branches. The junior authors conclude that this species is more properly a Zexmenia rather than an Otopappus. Geographical and morphological data are uti- lized to demonstrate that 0. australis, Z. columbiana, and Z. mikanjoides are conspecific. The latter two are considered Zexmenia mikanioides var. mikanioides, and the nomen- clatural combination is made to make 0. australis a variety of Z. mikanioides. The genus Otopappus Benth. belongs to the subtribe Verbesininae of the Heliantheae (Asteraceae) and contains about 15 species as presently understood (Hartman and Stuessy, unpubl.). Most taxa are found from western Mexico to Costa Rica. The closest generic relatives are Notoptera Urb. and Salmea DC. (Blake, 1915a; Stuessy, 1977). McVaugh (1972) suggested that the generic distinctiveness of Otopap- pus and Notoptera may be specious and recent revisionary studies (Hart- man and Stuessy, in prep.) have shown that the taxa are congeneric. The genus is unified by its viny habit and winged awns of the achenes. How- ever, one species, 0. australis, is isolated morphologically and geograph- ically. This taxon was originally described by Blake (1924) as a relative of 0. verbesinioides Benth. and as the first representative of the genus from South America. Features of the achenes of 0. australis differ from other species of the genus and suggest possible affinities with other gen- era. Geographically, 0. australis is known from Venezuela and Ecuador, which are outside the known range of all other species of the genus (0. simplex Badillo was also described from Venezuela, but it does not belong in Otopappus; details of that relationship will be described elsewhere). Interest in Otopappus australis has developed independently with the senior author finding material new to Panama, and the junior authors determining specific and generic relationships. Discovery of each other's work suggested that the observations and interpretations be published

A Systematic Study of the Genus Tetrachyron (Asteraceae: Heliantheae)

Abstract: Tetrachyron is a genus of five species restricted to eastern Mexico and northern Guatemala. Most previous treatments regard these species as members of various subgenera in the large polymorphic genus Calea. As a result of the various systematic techniques utilized in this study, the genus Tetrachyron is reestablished; it includes the subgenera Tephrocalea and Tetrachyron (in part). Diagnostic features for Tetrachyron are its shrubby habit, opposite, entire to serrulate margined leaves, sol- itary to corymbose capitulescences, and four-angled achenes which usually bear four pappus scales. Generally, these and other morphological, anatomical, and chemical features distinguish Tetrachyron from Calea and other allied genera. Tetrachyron Schlechtendal is a small genus of shrubs that occurs in eastern Mexico and Guatemala. Most species are unknown to the casual observer because of their uncommon occurrence and restricted distri- butions. Tetrachyron never has been studied intensively; the only taxo- nomic treatment produced for it is that by Robinson and Greenman (1896).

Herbarium Computerization at the University of Minnesota

Abstract: The computerization of label data in the University of Minnesota (MIN) Herbarium is described along with some of the advantages of using the data base management system called "System 2000." This system is very versatile, economical, easy to use and the data bases are directly transferrable to other institutions. So far all of the lichens in the MIN and ABSL herbaria have been computerized (about 48,000) and are in several data bases. Label data are keypunched on cards for entry and the arrangement and format of the data entered on the cards is presented. Of the numerous retrievals possible a few examples are described including computer generated distribution maps and local species lists. The computerization is progress- ing to other groups of plants and comments are presented about some of the prob- lems in such a project. As herbarium collections grow and as more kinds of information are desired from the collections, access to the information becomes more difficult. The new emphasis on area ecological studies for environmental impact studies often results in requests for data from herbaria that are very time consuming to produce. In other cases the herbarium contains information that is impossible to obtain for practical reasons. Storing the label data in a computer data base can provide quick, economical access to all of the label data and also can assist in the curatorial operations of the herbarium. The computer data base management system in use at the University of Minnesota Herbarium has proven to be well worth the effort in answering requests for local and state species lists and in pro- ducing reports for agencies funding floristic studies. It is described here as one example of an economical system which other herbaria may wish to use or modify for their own use. Several herbaria in the world have started computerizing the label data for different groups of plants and for special purposes. Some herbaria curators have computerized label data for all or parts of a complete

Taxonomy of the genus Amphiachyris (Asteraceae: Astereae)

Abstract: Amphiachyris is a North American genus of two species, A. dracunculoides and A. amoena. Related to Gutierrezia, it has in the past been placed in synonymy under that genus and also under Xanthocephalum. The generic status of A mphiachyris, as recognized by Solbrig, is accepted. Chromosome counts for both species and two species of Gutierrezia are reported. Counts of n = 4 for A. amoena and A. dracun- culoides and n 5 and n = 8 for G. texana are new. Preliminary chromatographic results indicate the presence of sulfated flavonoids in Amphiachyris. The genus Amphiachyris is composed of two annual species, one of which is restricted to the limestone-derived clay soils of the Edward's Plateau region of central Texas. The other, a very weedy species, is distributed widely on black prairie soils in the midwestern United States with scat- tered localities known as far east as South Carolina (Fig. 1). The distri- butions of Amphiachyris and of the annual species of Gutierrezia overlap throughout much of their ranges; these taxa are also quite similar in gross morphology. It is not surprising, therefore, that the taxonomic placement of Amphiachyris has been altered several times by various work- ers. The purpose of the present study is to evaluate the status of the taxon, using morphological, cytological and chemical methods.

Special Report: Status of the Flora of China

Abstract: It is well known that China is very rich in plant life, so the project, Flora of China, has attracted the attention of botanists all over the world. This article presents a brief report on the initiation, organization, compilation and publication of the Flora as well as some of the problems encountered in the process of its compilation. We would greatly appreciate suggestions and assistance from our colleagues of different countries in this undertaking. According to the preliminary estimates by the Chinese botanists, China has a diverse flora of approximately 30,000 species of plants including ferns, gymnosperms and angiosperms. The Flora of China will be comprised of 80 volumes, but since some volumes will be published in two separate parts, the total number of bound volumes will be 120. Owing to our current conditions and an inadequate number of trained botanists, the completion of such a monumental task is not easy. It should be noted that due to the historical background of China, there are some complicated factors involved in the compilation of the Flora. It is known to all that in the period from 1750 to approximately 1950, when China was in the feudal, semi-feudal and semi-colonial society, there were missionaries, soldiers, adventurers and even professional plant collectors from Western countries who came to China and collected a large quantity of plant specimens which were subsequently housed in their own herbaria. After being studied by the Western botanists, many new taxa of Chinese plants were published in American, British, French, German, Italian, Russian and Japanese journals. Thus the scientific information is widely scattered and more significantly, a large number of type specimens of Chinese plants are preserved in diverse herbaria. Consequently, difficulties have occurred for Chinese botanists in their work on identification and description. While there is currently an extensive effort being expended in the task of producing the Flora of China, we can proceed in the compilation of the project only by reviewing and assessing the work done by earlier foreign scholars. After liberation of this country, under the auspices of the Chinese Academy of Sciences, botanical institutions have been founded in Peking, Nanking, Canton, Keiling, Wuhan, Lushan, Chengtu, Kunming, Wuking, Shenyang, Sining and Urumchi. Research activities of phytotaxonomy, morphology, ecology, physiology, plant introduction and acclimatization, etc., are in progress in these institutions.

Intersectional Hybridization in Haplopappus: Blepharodon x Hazardia

Abstract: Interspecific hybrids between Haplopappus arenarius Benth. (n = 4) of section Blepharodon and H. squarrosus Hook. & Arn. (n = 5) of section Hazardia are vigorous but only 3.8% pollen fertile. However, pachytene analysis of microsporo- cytes shows that the chromosomes of the two species are highly homologous and differ primarily by translocations. Mean minimum chiasma frequency was reduced from that of the parents to 4.3 per cell. Both morphological similarity and cytoge- netic analyses indicate that the two sections should be considered congeneric. In a monographic study of Haplopappus, Hall (1928) treated Blephar- odon and Hazardia as sections of two phyletic lines that were based on involucre shape. However, some recent systematists have placed various species of Hall's Blepharodon in the genus Machaeranthera (Shinners, 1950, 1964; Hartman, 1976; Turner & Hartman, 1976) and other sec-

Artificial Hybridization in Hedeoma (Labiatae)

Abstract: Thirteen species of Hedeoma, representing three subgenera, and one species of Poliomintha were artificially crossed to attempt 52 hybrid combinations. Crossability was generally high, and 83% of the attempted hybridizations between species pairs were successful. Intrasubgeneric hybrids within the subgenus Sature- joides were the most easily obtained, whereas intersubgeneric and intergeneric hy- bridization attempts accounted for most of the crossing failures. Only nine F1 hybrids set viable seed, and almost all of these were intrasubgeneric crosses within subg. Saturejoides. Hybrid sterility is seemingly an important reproductive barrier in Hede- oma; translocations and inversions were among the observed meiotic irregularities. One nearly sterile hybrid was selfed to produce a relatively fertile F2 generation. Intercorrelation analysis of the F2 revealed significant correlations only among re- lated morphological characters and no significant correlations were found between morphology and pollen stainability. It is concluded that, at least in this instance, the barrier of hybrid sterility can be easily overcome and hybridization may be a source of naturally occurring interpopulational variation. Hedeoma in its most recent treatment (Irving, in press) consists of 38 species and five varieties. The genus is most abundantly represented in the American southwest and northern Mexico; five species are also rec- ognized for South America. Hedeoma comprises four subgenera, three of which were part of the present study. The subgenus Poliominthoides consists of shrubby desert species whose relationship to the more her- baceous members of Hedeoma and to the genus Poliomintha has long been questioned (Gray, 1878; Briquet, 1897; Epling & Stewart, 1939; Irving, in press). The subgenus Ciliatum is made up of caespitose perennials with relatively localized distributions. These form a morphologically dis- continuous unit in Hedeoma which may be best treated as a separate genus, as was done by Epling (1940). The subgenus Saturejoides houses the majority of the species of Hedeoma. Typically, members of this group are inbreeding, herbaceous perennials which are widespread in arid re- gions. Within subg. Saturejoides four xerophytic species groups have been discerned, each linked morphologically to a more restricted, outbreed- ing, montane species. It has been suggested by Irving (1976; in press) that the outbreeding species are ancestral for their respective complexes and evolved from a common stock subsequent to geographic separation. The inbreeding xerophytes, in turn, are believed to have evolved con- comitant with the formation of reproductive barriers, isolating them from their outbreeding ancestors.