William C. Dickison

A phylogenetic analysis of Cunoniaceae

We present a cladistic analysis of genera of Cunoniaceae based on 44 structural characters using Wagner parsimony. A synthetic outgroup based on the attributes of Hamamelidaceae, Rosaceae and Fagaceae was used to polarize character states and root resulting cladograms. In all of the resulting cladograms, a clade consisting of Gillbeea, Brunellia, Spiraeanthemum, and Aistopetalum formed the sister group of the rest of the Cunoniaceae. The continued recognition of Brunellia in a monogeneric family separate from Cunoniaceae was not supported by our results. The hypothesis that apocarpy was secondarily derived within the Cunoniaceae in Brunellia and Spiraeanthemum was supported. The sister group of the above set of taxa shared the derived possession of interpetiolar stipules (although they originated in parallel in the Spiraeanthemum-Aistopetalum group). The group defined by interpetiolar stipules, consisting of the bulk of the Cunoniaceae, includes Eucryphia and Bauera, which have been placed often in monotypic families. Eucryphia is the sister group of a clade defined by bicarpellate gynoecia, which are derived within Cunoniaceae. Bauera is a member of a clade of subshrubs that includes Acrophyllum and Anodopetalum. The southern hemisphere family Cunoniaceae is centered largely in eastern Australia, New Guinea, and New Caledonia with a few genera in southern Africa, Madagascar, and the neotropics. Cunoniaceae have been discussed as including the most primitive members of Rosidae. As such, the family was allied traditionally with Rosaceae and Saxifragaceae s.l. (Baillon 1871; Engler 1928a; Hutchinson 1959; Schulze-Menz 1964; Wettstein 1935). Kalkman (1988), for example, considered Cunoniaceae to be the most plausible sister group of Rosaceae. Ingle and Dadswell (1956) noted the resemblance of wood features among Cunoniaceae, Dilleniaceae and Theaceae. Takhtajan (1969) linked Rosidae to Dilleniales through Cunoniaceae. Recently, similarities have been re-emphasized between Cunoniaceae and certain basal Hamamelidae, particularly Hamamelidaceae (Dickison 1989). Hence, the Cunoniaceae appear positioned at a critical transitional point in the evolution of higher dicotyledonous groups (see also Ehrendorfer 1977; Ehrendorfer et al. 1984) and, therefore, assume considerable phylogenetic importance. Despite the key position of Cunoniaceae for understanding the radiation of higher dicotyledonous groups, numerous questions remain about patterns of character evolution and relationships within the family. This cladistic analysis of the genera of Cunoniaceae addresses these questions. Nineteen to 26 genera generally are circumscribed in the family. They are woody plants with decussate leaves and most have interpetiolar stipules. The decussate leaf arrangement has been hypothesized (Dickison and Rutishauser 1990; Kalkman 1988) to support the monophyly of Cunoniaceae. The genera have diverse inflorescence, flower and fruit forms which have created problems for understanding relationships within the family. A significant problem is the relationship of two problematic genera, Bauera and Eucryphia, to Cunoniaceae. Although often allied with Cunoniaceae (Bausch 1938; Dickison 1978; Hils 1989; Huber 1963; Jay 1968; Patel 1990; Planchon 1854), each is generally placed in a monotypic family. Both Bauera and Eucryphia have a decussate leaf arrangement. Eucryphia has interpetiolar stipules. Until recently, Bauera had been considered exstipulate; however, it has been shown to have paired, free stipules with the opposite leaves at each node (Dickison and Rutishauser 1990; Hils 1989). Dickison and Rutishauser (1990) hypothesized that both Bauera and Eucryphia are nested within Cunoniaceae as

Morphology and Anatomy of the Flower and Pollen of Saruma henryi Oliv., a Phylogenetic Relict of the Aristolochiaceae

DIcIusON, W. C. (Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280). Morphology and anatomy of the flower and pollen of Saruma henryi Oliv., a phylogenetic relict of the Aristolochiaceae. Bull. Torrey Bot. Club 119: 392-400. 1992.-A study of the floral morphology and anatomy and pollen morphology of the monotypic Chinese genus Saruma was undertaken to provide a more thorough diagnosis of the plant and make comparisons with other members of the Aristolochiaceae. The possession of well-developed petals, a gynoecium of partially separate carpels, follicular fruit, and a monosulcate form of pollen document the primitive position of the genus. Pollen is semitectate and reticulate with a stratified, columellate wall structure. The gynoecium is of particular phylogenetic interest and is composed of a primitive form of three-trace carpel with an elongated, pubescent stigmatic region that extends along the exposed ventral (adaxial) surface. Numerous ovules are borne in two longitudinally oriented, submarginal rows and are vascularized by traces arising from the ventral bundles. The pattern of floral vascularization is similar to other members of the Aristolochiaceae, exhibiting the tendency for extensive fusion of vascular bundles. Unlike other Aristolochiaceae, oil cells and calcium oxalate crystals are absent from floral tissues. Saruma also diverges from the Aristolochiaceae by possessing stamens that become recurved inward at maturity, creating a functionally introrse dehiscence. Reproductive morphology provides compelling evidences for the segregation of Saruma to a distinct subfamily within the Aristolochiaceae. There is little convincing evidence to indicate that Saruma and Asarum share a common ancestry.

The morphology and relationships ofMedusagyne (Medusagynaceae)

The comparative vegetative and reproductive morphology and anatomy of the endangered, monotypic, dicotyledonous genusMedusagyne was studied, and detailed descriptions of leaf, axis, nodal, wood, floral, pollen, fruit, and seed structure are presented. Overall, the genus has many specialized features, including the possession of extreme, habitat-related specializations. Flowers are either bisexual or staminate, and are interpreted as retaining some primitive aspects, such as many free parts spirally arranged on an elongate floral axis. One of the most salient structural features of the plant is the massive development of ensheathing fibrous elements around the vascular system of both vegetative and reproductive tissues. Diffuse foliar sclereids are absent. Particular attention is paid to the unusual multicarpellate, synovarial gynoecium and comparisons are made with theCaryocaraceae. The totality of morphological and anatomical evidence confirms the view thatMedusagyne is a very distinct and evolutionarily isolated genus, best treated as forming the monotypic familyMedusagynaceae. Observations are presented, including the occurrence of stamen fascicle traces, that link the family to the dillenialean and thealean assemblage. Like other isolated thealean taxa,Medusagyne shows affinities to several different families, without having especially close relationships with any particular extant taxon.

Wood Anatomy of the Styracaceae: Evolutionary and Ecological Considerations

Woods of over 40 species representing nine genera of Styracaceae were studied. Features present in most taxa include growth rings, diffuse porosity, combinations of both solitaries and pore multiples, exclusively scalariform perforation plates, opposite to alternate intervessel pitting, imperforate tracheary elements with indistinctly bordered pits, both uniseriate and multiseriate heterocellular rays, and axial parenchyma distributed as a combination of diffuse, diffuse-in-aggregates, and scanty. Prismatic crystals occur in species of the genera Bruinsmia, Halesia, and Styrax, and silica is present in a few Neotropical species of Styrax. The characteristic solitary pore distribution and high scalariform perforation plate bar number of Huodendron are of potential evolutionary significance. The xylem of Lissocarpa differs from the Styracaceae in possessing more highly evolved vessel elements with both simple and scalariform perforations and prominently banded axial parenchyma. The occurrence of simple perforation plates in the wider, earlywood vessel elements, along with an increased pore frequency and decreased vessel element length, in Styrax platanifolius and S. texanus is documented. Both species inhabit seasonally dry habitats of the southwestern United States, thus supporting similar specialisations observed in other plants growing in xerophytic conditions. The apparent variation in perforation plate condition within different geographic varieties of S. officinalis is discussed. Significant correlations of wood anatomical characters and latitude of provenance are present among species of Styracaceae. Increasing latitude is strongly correlated with increased pore and multiseriate ray frequency, and decreased vessel element length and wall thickness. Increasing latitude is less strongly correlated with an occurrence of decreased pore diameter, increased bar number per perforation plate, increased fibre-tracheid and intervessel pit diameter, and increased frequency of uniseriate rays. Weak correlations are also evident between increasing latitude and shorter ray height and narrower, shorter, and thinner-walled fibre-tracheids.

STRUCTURAL CORRELATIONS AMONG WOOD, LEAVES AND PLANT HABIT

Within the phylogenetically unrelated genera Hibbertia and Erythroxylum multiple correlations among woody anatomy, plant stature, and details of leaf morphology and anatomy are clearly environmentally related. Xeric radiants typically have undergone plant and leaf size reductions, along with the development of foliar xeromorphy, deciduousness, and xeromorphic xylem specializations. Mesic radiants have evolved an increased plant stature and leaf size as well as retaining a primitively mesomorphic xylem structure. Clinal variation patterns are much more extreme and apparent in Hibbertia whereas Erythroxylum species possess more subtle degrees of habitat related variability. In species of both genera, modifications in leaf morphology and anatomy and the existence of deciduousness, appear to buffer the xylem and permit rather primitive and mesomorphic wood anatomy to exist within seasonally or permanently dry locations. The extent of the buffering influence of leaves upon the xylem tissues is presumably determined by the complex interrelationships between various climatic variables and such features as leaf size, duration, type and degree of scleromorphy, as well as non-foliar characteristics such as architectual forms, degree of stem succulence, and the nature of the root system. In this regard the foliage constitutes perhaps the most significant component of the plant hydrovascular system. Biological and evolutionary interpretations of wood anatomy within an ecological context, therefore, are ill-advised in the absence of correlative leaf structural data.

A study of the floral morphology and anatomy of the Caryocaraceae.

(...) Important and previously unreported differences between the two genera are: ovules bitegmic in Caryocar, ovules unitegmic in Anthodiscus; styles simple in Caryocar; styles compound in Anthodiscus; and major variation in floral vascularization including the more extensive fusion of major traces in Anthrodiscus. Stamen fascicle traces are reported for the first time in the family, and in combination with other features, clearly link the family to the Theales. (...)

THE MORPHOLOGY AND RELATIONSHIPS OF ONCOTHECA BALANSAE1

The anatomy and morphology of vegetative and reproductive structures of the monotypic, dicotyledonous genus Oncotheca were studied to evaluate the systematic relationships of this New Caledonian endemic. Wood has remained at a low level of advancement, as evidenced by the solitary, angular pores and exclusively scalariform perforation plates. Imperforate tracheary elements are fiber tracheids, and axial parenchyma is diffuse to diffuse in aggregates in distribution. Sieve tube elements possess oblique to very oblique, compound sieve plates. Nodal anatomy is pentalacunar, and petioles contain a single, undissected arc of vascular tissue. A number of apparently xeromorphic leaf features, including general foliar coriaceousness, may result from the poor availability of soil minerals. Leaves are characterized by a thick cuticle, uniseriate epidermis with nearly anomocytic stomata having paracytic or tetracytic tendencies, and a bifacial mesophyll with two or three hypodermal layers. Foliar venation is brochidodromous. High-order venation is characterized by freely ending branched veinlets and imperfect areolation. Flowers are relatively advanced, as evidenced by extensive fusion of parts and the union of major floral bundles such as the ventral carpellary traces. A close relationship between Oncotheca and the Aquifoliaceae and Ebenaceae is refuted. Support is given to the elevation of the genus to familial status and its placement near the Theaceae.

Floral morphology and anatomy of Bonnetiaceae

DICKISON, W. C. (Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 275993280) and A. L. WEITZMAN (Department of Botany, Smithsonian Institution, Washington, DC 20560). Floral morphology and anatomy of Bonnetiaceae. J. Torrey Bot. Soc. 125:268-286. 1998.-A detailed study of floral morphology and anatomy of three genera comprising a narrowly circumscribed dicotyledonous family Bonnetiaceae is presented. Flowers are subtended by bracteoles and possess a perianth that is clearly differentiated into a 5-parted calyx and corolla composed of rather thick members. The androecium contains numerous stamens that are united at the base to form a short tube or collar or the stamens are pentadelphous and grouped at the base into five bundles that are positioned in the petal planes. Stamen fascicle traces are reported for the first time in flowers of Bonnetiaceae and are shown to originate close to, or adnate to, the median petal trace. Occasionally, two fascicle bundles arise side by side from a common gap as double bundles. Anther morphology and attachment is variable. Ploiarium possesses nectariferous discs that alternate with the stamen clusters. The presence of nectariferous tissue in Archytaea is variable. Nectaries can be supplied by double bundles, supporting the view that the nectaries of Plioarium and Archytaea represent transformed stamens. Gynoecia are compound, superior, and 3-carpellate or 5-carpellate. Styles range from divided to the base to undivided, and uniformly have a papillate stigma and a central canal filled with transfusion tissue. Placentation changes from axile to essentially parietal at midlevel of the ovary. Ovules are bitegmic, and contrasted with the putatively closely related Theaceae in which the elongated inner integument forms the micropyle, the outer integument projects well beyond the inner one. In addition to the degree of style fusion and carpel number, other important differences among genera of Bonnetiaceae are found in anther wall structure and floral vascular patterns. Major features of variation in the floral vascular system relate to the number and degree of independence of sepallary and petal traces; degree of independence of the androecial vascularization; the organization of the central ovarian vascular system; and the condition of the stylar vasculature. Comparisons are made among the flowers of Bonnetiaceae, Theaceae and Cluisiaceae.

Contributions to the morphology and anatomy of strasburgeria and a discussion of the taxonomic position of the strasburgeriaceae

A comprehensive study of floral and vegetative anatomy of the monotypic New Caledonian genusStrasburgeria Baillon was undertaken to provide a more thorough and accurate generic description, and to help clarify the evolutionary relationships of the plant. Detailed descriptions of leaf, stem, nodal, wood, floral, fruit, and seed morphology and anatomy are presented. In general, vegetative characters are primitive whereas those of the reproductive organs are regarded as advanced or specialized.Strasburgeria is envisioned as an early and independent offshoot from the thealean ancestral stock. It appears that the most appropriate treatment of the genus is to recognize the family Strasburgeriaceae and put it adjacent to the Ochnaceae in the current widely accepted manner.

Floral Morphology and Anatomy of Staphyleaceae

Five genera and 12 species of Staphyleaceae were examined with respect to systematic floral morphology and anatomy. Detailed descriptions of floral structure and vascularization are provided. Features of systematic and evolutionary importance in the family include the number and type of fusion of floral parts, placentation type, occurrence of a vascularized disk, and the degree of independence of floral vascular traces. Flowers of Tapiscia sinensis lack a disk, and the bicarpellate gynoecium, containing no internal ovarian septation, culminates a trend toward carpel fusion and reduction in ovular number that has resulted in a unilocular structure with a solitary ovule attached to a more derived basal or subbasal placenta. The progressive fusion of floral parts in the Staphyleaceae has been accompanied by the characteristic union of the androecial vascular supply and sepal-plane bundles, which subsequently divide to form an externally situated stamen vasculature and internal sepal strands. Huertea and Tapiscia deviate in a number of important respects from other genera of Staphyleaceae, and there is no doubt that Euscaphis, Turpinia, and Staphylea form one group of closely related genera and Huertea and Tapiscia another, more derived complex. Available evidence indicates that the Staphyleaceae are a natural assemblage, although the question whether the family should be subdivided into two subfamilies is unanswered. Staphyleaceae have their closest affinities with the cunonialean and particularly the saxifragalean complexes.