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Trochodendron aralioides. Diagram of bracts and residual perianth on the pedicel and receptacle of terminal and lateral anthetic flowers
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In the early development of Trochodendron aralioides (Trochodendraceae) inflorescences lateral flowers are initiated after the appearance of the floral pherophylls (subtending bracts). The terminal flower is preceded by metaxyphylls and is initiated earlier than the uppermost lateral flowers of the botryoid inflorescence. Small scales (interpreted...
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Raphiocarpus taygiangensis , a new species of Gesneriaceae family discovered in Tay Giang District, Quang Nam Province, Central Vietnam, is here described and illustrated. The new species is diagnosed by the combination of its stem up to 2 m long, sericeous hairs on young stem, leaf petiole and adaxial mid-vein, sparsely and minutely serrate leaf m...
Citations
... 9A, B). In extant Trochodendron tepals are observed in the flower, but they are ephemeral and do not leave prominent scars in fruit (Hsu, June & Chen, 2017). Eotrochion is distinguished from Concavistylon by more styles (Concavistylon has only four to eight) and styles that are variable in orientation (convex inward in some cases, outward in others) vs. consistently incurved in Concavistylon. ...
... The fossil genera are well supported as belonging to the Trochodendraceae clade by the possession of (1) laterally connate carpels, (2) capsular fruits comprising an aggregate of follicle-like units, (3) styles positioned laterally to basally on fruit and (4) each carpel dorsally nectariferous with a more or less circular nectar gland positioned below each of the styles. These four putative familial synapomorphies (see also , Doweld, 1998, Endress, 1986, 1993, Hsu et al., 2017, Nast & Baily, 1945Stevens, 2001 onward and Table 1) are obvious in both the extinct and extant taxa, but three additional synapomorphic features, i.e. the hair-pin course of the raphe in the seed, five vascular bundles per carpel and cortical vascular bundles in the flowering receptacle, are found in extant Trochodendron and Tetracentron, but remain undetermined for the fossil genera. The distinctive striato-reticulate ornamentation of the tricolpate pollen grains is probably another familial synapomorphy, but this character cannot be assessed in most of these fossils (except for Tetracentron fossils, see Chen, 2006 andGrímsson et al., 2008). ...
... Eotrochion, Concavistylon, Pentacentron and Tetracentron, which are united by the putative apomorphy of fruits with the styles more or less basally positioned, and racemose or spicate infructescences (with pedicels uniform in length; Fig. 8B-F). Trochodendron, in contrast, has fruits with more or less horizontally directed styles and a botryoid or thyrsoid infructescence ( Fig. 8A; with a terminal flower/fruit and frequently with cymose, three-flowered clusters on the basal branches; , Weberling, 1988, Hsu et al., 2017; also Trochodendron has a much reduced perianth, i.e. only a few, minute, triangular, bract-like structures and contains branched sclereids , Endress, 1986. ...
We present the oldest known occurrences of crown-group Trochodendraceae based on new material from the Palaeocene of Wyoming, USA. Two genera are recognized, Trochodendron and Eotrochion gen. nov. The fossil fruit of Trochodendron infernense sp. nov. is represented by a pedicellate, apically dehiscent capsular fruit composed of nine follicle-like units, each bearing a persistent convex style. The basal part is ornamented with numerous raised stamen scars. From the same deposits, Eotrochion is represented by infructescences, fruits and associated leaves. The infructescences are racemes of numerous apically dehiscent capsules, each with c. 14-16 styles, each with an underlying nectary and receptacles lacking stamen scars, but possessing a prominent perianth scar. A phylogenetic assessment of the modern species, plus representatives of four extinct genera of fossil Trochodendraceae based on available morphological characters, yields a favoured topology of Trochodendron(Eotrochion(Concavistylon kvacekii(C. wehrii (Pentacentron, Tetracentron)))). A parsimony analysis of currently available characters indicates that C. wehrii renders Concavistylon non-monophyletic. Accordingly, we transfer it to Paraconcavistylon gen. nov., characterized by pendent, rather than erect infructescences. We also reconsider the extinct Nordenskioeldia (Late Cretaceous to Miocene), the prior placement of which in Trochodendraceae has been challenged, and we consider it to fall outside the crown group of the family.
... This feature appears to be plastic in Eocene fruits. It is striking that this aspect of style structure is present in even young developing fruits of extant Trochodendron (Hsu et al. 2017: fig. 9E). ...
Two fossil fruit types and at least one fossil leaf type representing Trochodendraceae are recognized from the middle Miocene Cascadia flora of western Oregon, USA. Trochodendron rosayi sp. nov., known also from the middle Miocene of eastern Oregon and northern Idaho, is based on long-pedicelled, apically dehiscent capsular fruits with 7-9 persistent outcurved styles, very similar to the extant monotypic east Asian species T. aralioides. Concavistylon kvacekii gen. et sp. nov. is named for a racemose infructescence bearing shortly pedicellate, apically dehiscent capsules with 4 to 5 persistent incurved styles arising from the basal 1/3 of the fruit. Leaves associated at the Moose Mountain locality are recognized as Trochodendron postnastae sp. nov. They have basally acrodromous venation with a prominent midvein bracketed by a pair of strongly ascending basal secondaries and are thought to correspond to the T. rosayi fruits. These new occurrences demonstrate that greater diversity was present among fossil Trochodendraceae than previously recognized during the Miocene in western North America.
... A prominent perianth does not develop in Trochodendron flowers. Although a helix of 3-8 small scales appears during early ontogeny (Hsu et al. 2017), once shed they do not leave discernible scars on the fruit. Concavistylon wehrii, like the type species, C. kvacekii, lacks scars of stamens on the infructescences; in contrast, Trochodendron has numerous persistent, protruding staminal scars (text fig. ...
The Eocene flora of the Okanogan Highlands in the Pacific Northwest of North America has been recognized previously to include extinct species of both extant genera of the Trochodendraceae. Here, using microcomputed tomography (μCT) scanning to augment traditional methods, we recognize additional diversity, including two new fruit types. Concavistylon wehrii sp. nov. is documented by a fertile twig with attached leaves and an infructescence, allowing for an unusually complete reconstruction of this extinct genus. Concavistyon wehrii infructescences are racemes bearing fruits on short pedicels. Fruits are apically dehiscent capsules with four to six styles. The leaves resemble those of modern Trochodendron in pinnate venation, glandular teeth, and epidermal anatomy but have short petioles. The second new type of infructescence, Pentacentron sternhartae gen. et sp. nov., resembles extant Tetracentron in having small, sessile, apically dehiscent capsules but consistently has five, rather than four, styles. The μCT X-ray imaging demonstrates that fruits of both Concavistylon and Pentacentron differ from those of extant Trochodendraceae in having styles that are concave with stigmas directed inward rather than outward. These fossils, together with previously recognized fossil fruits and leaves of Trochodendron and leaves of Tetracentron from the same beds, indicate that the Trochodendraceae family was more diverse 50–52 Ma than it is today.
... We found 13-16 carpels in the material we studied, and the number is probably linked with the size and extension of the floral apex during growth, which might differ among individuals. The early development of the ovary resembles that found in genera of other families with similar multiple gynoecia, such as Trochodendron (Trochodendraceae), Gyrostemon (Gyrostemonaceae), Eucryphia (Cunoniaceae), Dillenia (Dilleniaceae), Actinidia (Actinidiaceae), Anthodiscus (Caryocaraceae), or Nymphaea (Nymphaeaceae) in the initiation of a ring of carpels surrounding a broad central meristem (Van Heel 1987;Dickison 1978Dickison , 1990cHufford 1996;Endress 1997Endress , 2001Bull-Hereñu et al. 2016;Hsu et al. 2017;K. Bull-Hereñu and L. P. Ronse De Craene, unpublished manuscript). ...
Premise of research. The floral development of the monotypic genus Medusagyne is investigated to understand the mechanisms of stamen and carpel increases in light of its proposed affinity with Ochnaceae. Methodology. Flowers at different stages of development were investigated with SEM. Pivotal results. Flowering shrubs are andromonoecious. Flowers arise in cymes at the end of shoots. Initiation of staminate and bisexual flowers is similar for sepals and petals, which arise in a spiral sequence. Stamen initiation is centrifugal on a broad circular primordium but becomes more or less irregular by the insertion of additional stamens between the older stamens. In staminate flowers the globular floral apex is completely covered with stamens, with no trace of carpels. Bisexual flowers emerge on the lower branches and develop a broad stamen ring surrounding a whorl of 13–16 carpels. Carpels initiate in a ring around the massive floral apex and develop mainly in a vertical direction. Carpels are progressively swamped in the stamen mass by a simultaneous expansion of filaments, and styles become irregularly compressed in older buds. The adaxial expansion of carpel tissue eventually overtops the floral apex as a roof. Measurements of buds show that carpel and stamen numbers are linked with the proportional size of the floral apex relative to the whole size of the flower bud.
Conclusions. The unusual floral development of Medusagyne supports the separation of the genus in its own family, although several characters link it with the Ochnaceae clade. Stamen initiation and expansion shows much similarity with Eucryphia in Cunoniaceae. It is suggested that the larger number of carpels is intimately linked with the higher stamen numbers. Constraints of space and a vertical growth pattern of the floral apex cause the peculiar morphology of the gynoecium and the variably delayed stamen initiation.
... The carpel flanks are congenitally fused. In the upper part of the ovary a compitum is formed by post genital fusion of the carpels in the center, while in the lower portion of the gynoecium the carpels do not meet in the center, but form a central dome Endress 1986, Hsu et al. 2017. The pollen grains are spheroidal and tricolpate with striate-reticulate exine. ...
Two new fossil taxa referable to the basal eudicot grade are described from the Kamikitaba locality (ca. 89 MYBP, early Coniacian: Late Cretaceous) of the Futaba Group in Japan. These charcoalified mesofossils exhibit well-preserved three-dimensional structure and were analyzed using synchrotron-radiation X-ray microtomography to document their composition and internal structure. Cathiaria japonica sp. nov. is represented by infructescence segments that consist of an axis bearing three to four fruits. The capsular fruits are sessile and dehiscent and consist of a gynoecium subtended by a bract. No perianth parts are present. The gynoecium is monocarpellate containing two pendulous seeds. The carpel is ascidiate in the lower half and conduplicate in the upper part, and the style is deflected abaxially with a large, obliquely decurrent stigma. Pollen grains are tricolpate with a reticulate exine. The morphological features of Cathiaria are consistent with an assignment to the Buxaceae s. l. (including Didymelaceae). Archaestella verticillatus gen. et sp. nov. is represented by flowers that are small, actinomorphic, pedicellate, bisexual, semi-inferior, and multicarpellate. The floral receptacle is cup shaped with a perigynous perianth consisting of several tepals inserted around the rim. The gynoecium consists of a whorl of ten conduplicate, laterally connate but distally distinct carpels with a conspicuous dorsal bulge, including a central cavity. The styles are short, becoming recurved with a ventrally decurrent stigma. Seeds are ca. 10 per carpel, marginal, pendulous from the broad, oblique summit of the locule. Pollen grains are tricolpate with a reticulate exine pattern, suggesting a relationship to eudicots. The morphological features of Archaestella indicate a possible relationship to Trochodendraceae in the basal grade of eudicots. The fossil currently provides the earliest record of the family and documents the presence of Trochodendraceae in eastern Eurasia during the middle part of the Late Cretaceous.
