Pattern analysis in pseudanthia

Pseudanthia occur in more than 40 angiosperm families. With regard to the underlying inflorescence structure they can be classified into the following groups: (a) floral and (b) hyperfloral pseudanthia, each with (c) or without (d) pseudocorollas. Pseudanthia have developed along independent evolutionary lines and are not bound to a particular inflorescence structure. They are the result of (a) the specific morphological predisposition of the taxon concerned, (b) aggregation and diminution of the flowers, giving rise to the formation of an attraction unit (for animal pollination), (c) variation, and (d) selection. Ontogenetical abbreviation is regarded to play an essential role in the origin and elaboration of pseudanthia.Full-length version of a paper read at the 14th International Botanical Congress, Berlin 1987, Symposium 4–19.     

Functional Monoecy Due to Delayed Anther Dehiscence: A Novel Mechanism in Pseuduvaria mulgraveana (Annonaceae)

Unlike most genera in the early-divergent angiosperm family Annonaceae, Pseuduvaria exhibits a diversity of floral sex expression. Most species are structurally andromonoecious (or possibly androdioecious), although the hermaphroditic flowers have been inferred to be functionally pistillate, with sterile staminodes. Pseuduvaria presents an ideal model for investigating the evolution of floral sex in early-divergent angiosperms, although detailed empirical studies are currently lacking. The phenology and pollination ecology of the Australian endemic species Pseuduvaria mulgraveana are studied in detail, including evaluations of floral scent chemistry, pollen viability, and floral visitors. Results showed that the flowers are pollinated by small diurnal nitidulid beetles and are protogynous. Pollen from both hermaphroditic and staminate flowers are shown to be equally viable. The structurally hermaphroditic flowers are nevertheless functionally pistillate as anther dehiscence is delayed until after petal abscission and hence after the departure of pollinators. This mechanism to achieve functional unisexuality of flowers has not previously been reported in angiosperms. It is known that protogyny is widespread amongst early-divergent angiosperms, including the Annonaceae, and is effective in preventing autogamy. Delayed anther dehiscence represents a further elaboration of this, and is effective in preventing geitonogamy since very few sexually mature flowers occur simultaneously in an individual. We highlight the necessity for field-based empirical interpretations of functional floral sex expression prior to evaluations of evolutionary processes.     

Evolution of endoapertures in early-divergent eudicots, with particular reference to pollen morphology in Sabiaceae

Endoapertures, the inner openings of compound apertures in pollen grains, are common in eudicots, but occur infrequently in early-divergent eudicot lineages, in which they are restricted to three families: Menispermaceae, Sabiaceae and Buxaceae. Pollen of Sabiaceae was examined using light, scanning and transmission electron microscopy. The endoapertures are large and lalongate, and intine onci are associated with their development. Optimisation of endoapertures onto an existing angiosperm phylogeny indicates that endoapertures have evolved at least three times independently: in Menispermaceae, in Sabiaceae plus Buxaceae (or possibly separately in these two families), and in the core eudicot clade. Sabiaceae are unusual among early-divergent eudicots in that they possess some characters that are more common in core eudicots, including pollen with endoapertures and pentamerous flowers. This indicates either that they are more closely related to core eudicots than is indicated by current molecular evidence, or that these characters are homoplastic. The latter would suggest a high degree of experimentation prior to evolutionary canalisation of some key morphological features in eudicots. The evolution of endoapertures in early-divergent eudicots is probably associated with possession of endexine sculpture (endosculpture) such as endocracks; endoapertures may have been retained in eudicots as a harmomegathic mechanism.     

Comparative ontogeny of the cyathium in Euphorbia (Euphorbiaceae) and its allies: exploring the organ-flower-inflorescence boundary

We present a detailed comparative ontogenetic analysis of pseudanthia of representatives of all three subtribes of Euphorbieae (Euphorbiinae, Neoguillauminiinae, Anthosteminae) in order to clarify their homologies and interpretation. The cyathium of Euphorbia and its allies (subtribe Euphorbiinae) closely resembles a bisexual flower but is traditionally interpreted as an inflorescence bearing clusters of highly reduced male flowers surrounding a single terminal female flower. Previously unreported characters are (1) male flowers formed one above the other in the male inflorescences of some Euphorbiinae, (2) late-developing perianthlike structures in some male flowers of Neoguillauminia cleopatra, (3) evidence for a bracteate origin of the female perianth in Anthosteminae and Neoguillauminiinae, and (4) spatiotemporally independent formation of abscission zone and perianth. Indistinct boundaries between inflorescence, flower, and floral organs demonstrate that defining the cyathium neither as an inflorescence nor as a flower is entirely satisfactory and indicate a "hybrid" flower/inflorescence nature of the cyathium. Based on our current knowledge and the existing phylogenetic context, it is most parsimonious to suggest that the cyathium evolved from a determinate thyrse with a terminal female flower surrounded by dichasial male partial inflorescences. We speculate that the cyathium was formed because of strong condensation and possible overlap between expression zones of regulatory genes.     

Nonflowers near the base of extant angiosperms? Spatiotemporal arrangement of organs in reproductive units of Hydatellaceae and its bearing on the origin of the flower

Reproductive units (RUs) of Trithuria, the sole genus of the early-divergent angiosperm family Hydatellaceae, are compared with flowers of their close relatives in Cabombaceae (Nymphaeales). Trithuria RUs combine features of flowers and inflorescences. They differ from typical flowers in possessing an "inside-out" morphology, with carpels surrounding stamens; furthermore, carpels develop centrifugally, in contrast to centripetal or simultaneous development in typical flowers. Trithuria RUs could be interpreted as pseudanthia of two or more cymose partial inflorescences enclosed within an involucre, but the bractlike involucral phyllomes do not subtend partial inflorescences and hence collectively resemble a typical perianth. Teratological forms of T. submersa indicate a tendency to fasciation and demonstrate that the inside-out structure-the primary feature that separates RUs of Hydatellaceae from more orthodox angiosperm flowers-can be at least partially modified, thus producing a morphology that is closer to an orthodox flower. The Trithuria RU could be described as a "nonflower", i.e., a structure that contains typical angiosperm carpels and stamens but does not allow recognition of a typical angiosperm flower. The term nonflower could combine cases of secondary loss of flower identity and cases of a prefloral condition, similar to those that gave rise to the angiosperm flower. Nonhomology among some angiosperm flowers could be due to iterative shifts between nonfloral construction and flower/inflorescence organization of reproductive organs. Potential testing of these hypotheses using evolutionary-developmental genetics is explored using preliminary data from immunolocalization of the floral meristem identity gene LEAFY in T. submersa, which indicated protein expression at different hierarchical levels.     

Defining the limits of flowers: the challenge of distinguishing between the evolutionary products of simple versus compound strobili

Recent phylogenetic reconstructions suggest that axially condensed flower-like structures evolved iteratively in seed plants from either simple or compound strobili. The simple-strobilus model of flower evolution, widely applied to the angiosperm flower, interprets the inflorescence as a compound strobilus. The conifer cone and the gnetalean ‘flower’ are commonly interpreted as having evolved from a compound strobilus by extreme condensation and (at least in the case of male conifer cones) elimination of some structures present in the presumed ancestral compound strobilus. These two hypotheses have profoundly different implications for reconstructing the evolution of developmental genetic mechanisms in seed plants. If different flower-like structures evolved independently, there should intuitively be little commonality of patterning genes. However, reproductive units of some early-divergent angiosperms, including the extant genus Trithuria (Hydatellaceae) and the extinct genus Archaefructus (Archaefructaceae), apparently combine features considered typical of flowers and inflorescences. We re-evaluate several disparate strands of comparative data to explore whether flower-like structures could have arisen by co-option of flower-expressed patterning genes into independently evolved condensed inflorescences, or vice versa. We discuss the evolution of the inflorescence in both gymnosperms and angiosperms, emphasising the roles of heterotopy in dictating gender expression and heterochrony in permitting internodal compression.     

Integrating Early Cretaceous fossils into the phylogeny of living angiosperms:Magnoliidae and eudicots

Over the past 25 years, discoveries of Early Cretaceous fossil flowers, often associated with pollen and sometimes with vegetative parts, have revolutionized our understanding of the morphology and diversity of early angiosperms. However, few of these fossils have been integrated into the increasingly robust phylogeny of living angiosperms based primarily on molecular data. To remedy this situation, we have used a morphological dataset for living basal angiosperms (including basal eudicots and monocots) to assess the most parsimonious positions of early angiosperm fossils on cladograms of Recent plants, using constraint trees that represent the current range of hypotheses on higher-level relationships, and concentrating on Magnoliidae (the clade including Magnoliales, Laurales, Canellales, and Piperales) and eudicots. In magnoliids, our results confirm proposed relationships of Archaeanthus (latest Albian?) to Magnoliaceae, Endressinia (late Aptian) to Magnoliales (the clade comprising Degeneria, Galbulimima, Eupomatia, and Annonaceae), and Walkeripollis pollen tetrads (late Barremian?) to Win-teraceae, but they indicate that Mauldinia (early Cenomanian) was sister to both Lauraceae and Hernandiaceae rather than to Lauraceae alone. Among middle Albian to early Cenomanian eudicots, we confirm relationships of Nelumbites to Nelumbo, platanoid inflorescences and Sapindopsis to Platanaceae, and Spanomera to Buxaceae. With the possible exception of Archaeanthus, these fossils are apparently not crown group members of living families but rather stem relatives of one or more families.     

Studies of Pollen Morphology and Its Systematic Position in the Order Piperales

The pollen morphology of 25 species and 10 genera of Piperales (Chloranthaceae, Piperaceae and Saururaceae) has been examined under light microscope, of which 7 species were observed under scanning electron microscope and 1 species, Hedyosmum orentale Merr. & Chun transmision electron microseope. Three principal types of pollen were found: anasulcate (mostly) (sometime trichotomosulcate), inaperturate (partly) and multicolpoidate (partly). The present article has discussed the palynological data mainly in relation to the classification and the systematic position of Cbloranthaceae and also deals with the systematic position of the order Piperales. The present author agrees to put the family Chloranthaceae into the order Piperales. Because this family differs from Piperaceae and Saururaceae in pollen morphology, therefore, Chloranthaceae should raise to the level of suborder. Among three families of the order Piperales, the present author considers Chloranthaceae to be the most primitive family, on account of the following reasons: 1. The family Chloranthaceae shows the characteristics of primitive entomophilous plants in the sculpture of exine, while in the other two families, Piperaceae and Saururaceae, their exine is almost smooth and represents wind-pollenated plants; 2. Pollen of the family Chloranthaceae are larger than those of Piperaceae and Saururaceae; 3. The fossil pollen Clavatipollenites has been proved to be one of the most primitive angiosperms on the earth, that it is known, it occurred in the early Cretaceous, and at that time ferns and gymnosperms were predominant, while the Chloran- thaceae has already existed at that time; 4. Sarcandra of Chloranthaceae possesses the characters of a vesselless secondary xylem and a delayed development of embryo. Thus, Chloranthaceae would be considered as the most primitive family in the order Piperales. The systematic position of the order Piperales is also discussed. Itutehinson makes a point that order Ranales is more primitive than Piperales, and his system is arranged in the following order: Ranales → Piperales → to climax family Chloranthaceae. This view-point, however, is net supported by the palynological data. Pollen morphology shows that Piperales is more primitive than Ranales, because the pollen in Piperales possess the ancient aperture type of Pteridospermes, i.e., the type of anasulcate aperture is prevailing in Piperales, moreover, pollen grains of Ranales are mainly tricolpate type, and tricolpate pollen is a characteristic of typical angiosperms. In addition, the Piperales possesses a series of characters that are common among monocots, but rare among dicots. As the divergence between dicer and monocot took place in the early Cretaceous, their ancestor possesses common chararcters both of dicots and monocots while the extant Piperales still possess many characters of monocots that indicate it is much nearer to the point of divergence, and it explains that the Piperales is closely related to the ancestor of monocots and dicers Piperales, therefore, is more primitive than Ranales.     

Racemose inflorescences of monocots: structural and morphogenetic interaction at the flower/inflorescence level

Background

Understanding and modelling early events of floral meristem patterning and floral development requires consideration of positional information regarding the organs surrounding the floral meristem, such as the flower-subtending bracts (FSBs) and floral prophylls (bracteoles). In common with models of regulation of floral patterning, the simplest models of phyllotaxy consider only unbranched uniaxial systems. Racemose inflorescences and thyrses offer a useful model system for investigating morphogenetic interactions between organs belonging to different axes.

Scope

This review considers (1) racemose inflorescences of early-divergent and lilioid monocots and their possible relationship with other inflorescence types, (2) hypotheses on the morphogenetic significance of phyllomes surrounding developing flowers, (3) patterns of FSB reduction and (4) vascular patterns in the primary inflorescence axis and lateral pedicels.

Conclusions

Racemose (partial) inflorescences represent the plesiomorphic condition in monocots. The presence or absence of a terminal flower or flower-like structure is labile among early-divergent monocots. In some Alismatales, a few-flowered racemose inflorescence can be entirely transformed into a terminal ‘flower’. The presence or absence and position of additional phyllomes on the lateral pedicels represent important taxonomic markers and key features in regulation of flower patterning. Racemose inflorescences with a single floral prophyll are closely related to thyrses. Floral patterning is either unidirectional or simultaneous in species that lack a floral prophyll or possess a single adaxial floral prophyll and usually spiral in the outer perianth whorl in species with a transversely oriented floral prophyll. Inhibitory fields of surrounding phyllomes are relevant but insufficient to explain these patterns; other important factors are meristem space economy and/or the inhibitory activity of the primary inflorescence axis. Two patterns of FSB reduction exist in basal monocots: (1) complete FSB suppression (cryptic flower-subtending bract) and (2) formation of a ‘hybrid’ organ by overlap of the developmental programmes of the FSB and the first abaxial organ formed on the floral pedicel. FSB reduction affects patterns of interaction between the conductive systems of the flower and the primary inflorescence axis.     

Molecular evolution of the petal and stamen identity genes, APETALA3 and PISTILLATA, after petal loss in the Piperales

Organ loss is an evolutionary phenomenon commonly observed in all kinds of multicellular organisms. Across the angiosperms, petals have been lost several times over the course of their diversification. We examined the evolution of petal and stamen identity genes in the Piperales, a basal lineage of angiosperms that includes the perianthless (with no petals or sepals) families Piperaceae and Saururaceae as well as the Aristolochiaceae, which exhibit a well-developed perianth. Here, we provide evidence for relaxation of selection on the putative petal and stamen identity genes, homologs of APETALA3 and PISTILLATA, following the loss of petals in the Piperales. Our results are particularly interesting as the B-class genes are not only responsible for the production of petals but are also central to stamen identity, the male reproductive organs that show no modification in these plants. Relaxed purifying selection after the loss of only one of these organs suggests that there has been dissociation of the functional roles of these genes in the Piperales.     

The evolution of ovule number and flower size in wind-pollinated plants

In angiosperms, ovules are "packaged" within individual flowers, and an optimal strategy should occur depending on pollination and resource conditions. In animal-pollinated species, wide variation in ovule number per flower occurs, and this contrasts with wind-pollinated plants, where most species possess uniovulate flowers. This pattern is usually explained as an adaptive response to low pollen receipt in wind-pollinated species. Here, we develop a phenotypic model for the evolution of ovule number per flower that incorporates the aerodynamics of pollen capture and a fixed resource pool for provisioning of flowers, ovules, and seeds. Our results challenge the prevailing explanation for the association between uniovulate flowers and wind pollination. We demonstrate that when flowers are small and inexpensive, as they are in wind-pollinated species, ovule number should be minimized and lower than the average number of pollen tubes per style, even under stochastic pollination and fertilization regimes. The model predicts that plants benefit from producing many small inexpensive flowers, even though some flowers capture too few pollen grains to fertilize their ovules. Wind-pollinated plants with numerous flowers distributed throughout the inflorescence, each with a single ovule or a few ovules, sample more of the airstream, and this should maximize pollen capture and seed production.     

Integrating Early Cretaceous fossils into the phylogeny of living angiosperms: Magnoliidae and eudicots

Over the past 25 years, discoveries of Early Cretaceous fossil flowers, often associated with pollen and sometimes with vegetative parts, have revolutionized our understanding of the morphology and diversity of early angiosperms. However, few of these fossils have been integrated into the increasingly robust phylogeny of living angiosperms based primarily on molecular data. To remedy this situation, we have used a morphological data set for living basal angiosperms (including basal eudicots and monocots) to assess the most parsimonious positions of early angiosperm fossils on cladograms of Recent plants, using constraint trees that represent the current range of hypotheses on higher-level relationships, and concentrating on Magnoliidae (the clade including Magnoliales, Laurales, Canellales, and Piperales) and eudicots. In magnoliids, our results confirm proposed relationships of Archaeanthus (latest Albian?) to Magnoliaceae, Endressinia (late Aptian) to Magnoliales (the clade comprising Degeneria, Galbulimima, Eupomatia, and Annonaceae), and Walkeripollis pollen tetrads (late Barremian?) to Winteraceae, but they indicate that Mauldinia (early Cenomanian) was sister to both Lauraceae and Hernandiaceae rather than to Lauraceae alone. Among middle Albian to early Cenomanian eudicots, we confirm relationships of Nelumbites to Nelumbo, platanoid inflorescences and Sapindopsis to Platanaceae, and Spanomera to Buxaceae. With the possible exception of Archaeanthus, these fossils are apparently not crown group members of living families but rather stem relatives of one or more families.     

Morphology of Hydatellaceae, an anomalous aquatic family recently recognized as an early-divergent angiosperm lineage

The family Hydatellaceae was recently reassigned to the early-divergent angiosperm order Nymphaeales rather than the monocot order Poales. This dramatic taxonomic adjustment allows comparison with other early-divergent angiosperms, both extant and extinct. Hydatellaceae possess some monocot-like features that could represent adaptations to an aquatic habit. Ecophysiological parallels can also be drawn from fossil taxa that are known from small achene-like diaspores, as in Hydatellaceae. Reproductive units of Hydatellaceae consist of perianthlike bracts enclosing several pistils and/or stamens. In species with bisexual reproductive units, a single unit resembles an "inside-out" flower, in which stamens are surrounded by carpels that are initiated centrifugally. Furthermore, involucre development in Trithuria submersa, with delayed growth of second whorl bracts, resembles similar delayed development of the second perianth whorl in Cabomba. Several hypotheses on the homologies of reproductive units in Hydatellaceae are explored. Currently, the most plausible interpretation is that each reproductive unit represents an aggregation of reduced unisexual apetalous flowers, which are thus very different from flowers of Nymphaeales. Each pistil in Hydatellaceae is morphologically and developmentally consistent with a solitary ascidiate carpel. However, ascidiate carpel development, consistent with placement in Nymphaeales, is closely similar to pseudomonomerous pistil development as in Poaes.     

An Appraisal of Range and Evolutionary Significance of Flower-Beetle Association,with Special Reference to Sap Beetles (Coleoptera: Nitidulidae)

A range of beetle species are associated with plants and many of them reside primarily in flowers; of these Nitidulidae possess a large share. Beetles which thrive upon angiosperms exhibited a rapid rate of speciation as compared to others with different feeding habits. Hence, beetles and angiosperms have co-evolved and influenced each others’ evolution for better survival. Some flower-visiting beetles have developed special features for floral diet and other purposes like pollination, shelter, reproduction, etc. Likewise, certain flowers also have adapted structurally and physiologically to attract beetles for pollination which include pollen, nectar, floral heat etc. Although beetles are found to be amongst the pioneer flower visitors, they are not as efficient pollinator as bee and butterfly. However, they have been found to be chief pollinators for a few plant families like Magnoliaceae, Annonaceae and Palmae. Several sap beetles have been encountered in floral parts in West Bengal, Assam, Uttar Pradesh, Karnataka and Tripura. Nature of relationships of those beetles with inflorescence and flowers were examined. None of them is yet found to be a true pollinator.     

被子植物雌全同株性系统:系统演化、性表达与进化意义

雌全同株是指雌花和两性花共同发生在同一植株上的性表达形式。作为被子植物从雌雄同花(两性花)向雌雄同株异花进化的一个重要阶段,雌全同株性系统在减少昆虫对雌性的取食和伤害、提高异交率以减少近交衰退、减少雌/雄功能干扰、提高雌/雄性功能间资源分配的灵活性,以及吸引传粉者等方面具有重要的进化适应意义。根据APG III分类系统,雌全同株性系统在被子植物木兰分支(magnoliids)的短蕊花科、单子叶植物分支(monocots)的天南星科和禾本科,以及核心真双子叶植物分支(core eudicots)中的菊科、苋科、唇形科和石竹科等23科中均有报道,且以菊科植物中最多。雌全同株植物不同类群的雌花和两性花在位置、形态、大小及开花时间等性表达特征上表现出多样化,且这些特征不仅受遗传因子的调控,还受可获得资源(如营养、光照、温度和水分等条件)的制约。该文针对我国对雌全同株性系统的研究还相对较少的现状,重点对具雌全同株性系统的类群在被子植物中的分布与系统演化、性表达与环境的关系等方面进行了分析与总结,并对有关其进化适应意义的5个假说进行了介绍和评价,对今后的研究方向进行了展望,以期为推动我国对被子植物雌全同株性系统的进化式样与机制研究提供理论资料。     

Floral color change: a widespread functional convergence

Ontogenetic color changes in fully turgid flowers are widespread throughout the angiosperms, and in many cases are known to provide signals for pollinators. A broad survey of flowering plants demonstrates that such color changes appear in at least 77 diverse families. Color-changing taxa occur commonly within what are considered derived lineages, and only rarely in early or primitive groups. The pattern of distribution of floral color change across orders, families, genera, and species demonstrates that the occurrence of the phenomenon within a group is not simply a result of phylogenetic history. Color changes can affect the whole flower or they can be localized, affecting at least nine floral parts or regions. The scale of color change (localized or whole-flower) is broadly correlated with the type of pollinator that characteristically visits the plant. Color changes can come about through seven distinct physiological mechanisms, involving anthocyanins, carotenoids, and betalains. Color changes due to appearance of anthocyanin are the most common, occurring in 68 families. Floral color change has clearly evolved independently many times, most likely in response to selection by visually oriented pollinators, and reflects a widespread functional convergence within the angiosperms.     

Organization of the root apical meristem in angiosperms

Although flowers, leaves, and stems of the angiosperms have understandably received more attention than roots, the growing root tips, or root apical meristems (RAMs), are organs that could provide insight into angiosperm evolution. We studied RAM organization across a broad spectrum of angiosperms (45 orders and 132 families of basal angiosperms, monocots, and eudicots) to characterize angiosperm RAMs and cortex development related to RAMs. Types of RAM organization in root tips of flowering plants include open RAMs without boundaries between some tissues in the growing tip and closed RAMs with distinct boundaries between apical regions. Epidermis origin is associated with the cortex in some basal angiosperms and monocots and with the lateral rootcap in eudicots and other basal angiosperms. In most angiosperm RAMs, initials for the central region of the rootcap, or columella, are distinct from the lateral rootcap and its initials. Slightly more angiosperm families have exclusively closed RAMs than exclusively open RAMs, but many families have representatives with both open and closed RAMs. Root tips with open RAMs are generally found in angiosperm families considered sister to other families; certain open RAMs may be ancestral in angiosperms.     

From Forgotten Taxon to a Missing Link? The Position of the Genus Verhuellia (Piperaceae) Revealed by Molecules

BACKGROUND AND AIMS: The species-poor and little-studied genus Verhuellia has often been treated as a synonym of the genus Peperomia, downplaying its significance in the relationships and evolutionary aspects in Piperaceae and Piperales. The lack of knowledge concerning Verhuellia is largely due to its restricted distribution, poorly known collection localities, limited availability in herbaria and absence in botanical gardens and lack of material suitable for molecular phylogenetic studies until recently. Because Verhuellia has some of the most reduced flowers in Piperales, the reconstruction of floral evolution which shows strong trends towards reduction in all lineages needs to be revised. METHODS: Verhuellia is included in a molecular phylogenetic analysis of Piperales (trnT-trnL-trnF and trnK/matK), based on nearly 6000 aligned characters and more than 1400 potentially parsimony-informative sites which were partly generated for the present study. Character states for stamen and carpel number are mapped on the combined molecular tree to reconstruct the ancestral states. KEY RESULTS: The genus Peperomia is generally considered to have the most reduced flowers in Piperales but this study shows that this is only partially true. Verhuellia, with almost equally reduced flowers, is not part of or sister to Peperomia as expected, but is revealed as sister to all other Piperaceae in all analyses, putting character evolution in this family and in the perianthless Piperales in a different light. A robust phylogenetic analysis including all relevant taxa is presented as a framework for inferring patterns and processes of evolution in Piperales and Piperaceae. CONCLUSIONS: Verhuellia is a further example of how a molecular phylogenetic study can elucidate the relationships of an unplaced taxon. When more material becomes available, it will be possible to investigate character evolution in Piperales more thoroughly and to answer some evolutionary questions concerning Piperaceae.     

Establishing a fossil record for the perianthless Piperales: Saururus tuckerae sp. nov. (Saururaceae) from the Middle Eocene Princeton Chert

Investigations of small permineralized flowers from the Middle Eocene Princeton Chert, British Columbia, Canada have revealed that they represent an extinct species of Saururus. Over 100 flowers and one partial inflorescence were studied, and numerous minute perianthless flowers are borne in an indeterminate raceme. Each flower is subtended by a bract, and flowers and bracts are borne at the end of a common stalk. Five stamens are basally adnate to the carpels. Pollen is frequently found in situ in the anthers. Examined under SEM and TEM, pollen grains are minute (6-11 μm), monosulcate, boat-shaped-elliptic, with punctate sculpturing and a granulate aperture membrane. The gynoecium is composed of four basally connate, lobed carpels with recurved styles and a single ovule per carpel. Flower structure and pollen are indicative of Saururaceae (Piperales), and in phylogenetic analyses using morphological characters, the fossils are sister to extant Saururus. The fossil flowers are described here as Saururus tuckerae sp. nov. These fossil specimens add to the otherwise sparse fossil record of Piperales, represent the oldest fossils of Saururaceae as well as the first North American fossil specimens of this family, and provide the first evidence of saururaceous pollen in the fossil record.