New observations on the Lower Carboniferous pteridosperm Diplopteridium Walton and an associated synangiate organ

New material of Diplopteridium holdenii is described from the Drybook Sandstone assemblage of Upper Visean (Middle Mississippian) age at Puddlebrook, Gloucestershire. Vegetative leaves consist of bifurcate fronds which are pinnately divided and terminate in narrow pinnule segments. The fronds are arranged spirally in terminal crowns on a narrow, spindly axis. Fertile leaves consist of fronds which bear a median, dichotomous branchlet which gives rise to reflexed, bilaterally symmetrical cupules. One specimen demonstrates that a single fertile crown consisted of cupulate and vegetative fronds. The detailed morphology of the cupules is reconstructed from compression/impression and fusainized material from both attached and isolated units. An isotomously branched synangiate organ is also described from the locality. The synangiate organ is assigned to a new genus and species. A comparison of D. holdenii and this synangiate organ with Diplopteridium teilianum from north Wales and Sphenopteris bifida and Sphenopteris affine from northern England and Scotland, provides indirect evidence that the synangiate organ may have belonged to D. holdenii . Bifurcate and trifurcate fronds associated with dichotomous branchlets bearing either synangial or cupulate structures was a common association in the Visean compression assemblages of Great Britain.     

Reconstructing the Pennsylvanian-Age Filicalean Fern Botryopteris tridentata (Felix) Scott

Numerous anatomically preserved fragments of the Middle Pennsylvanian age filicalean fern, Botryopteris tridentata, occur in coal balls collected at the Pittsburgh and Midway Coal Company mine near Baxter Springs, Kansas. Included are the first fertile specimens of the species, evidence of complete vegetative frond architecture, and fronds that are specialized for vegetative propagation. Rhizomes are erect and unbranched, have helical phyllotaxis and short internodes, and typically display an ectophloic solenostele. Fronds are tripinnately compound with lobed pinnules that have open, dichotomous venation. Fertile pinnae or individual pinnules are interspersed among vegetative frond segments and produce sori of annulate sporangia beneath veins on the abaxial pinnule surface. Fertile pinnule lobes are rolled toward the abaxial surface to enclose the sori. Sporangia have a horizontally elongated biseriate annulus located near the short broad stalk and produce tetrahedral-shaped trilete spores with coarse spines. Epiphyllous branches diverge from the stipe or rachis, and some fronds produce only branches. This fern is reconstructed as having short stems. Helically arranged fronds are either pinnately dissected with lobed vegetative pinnules and abaxially rolled fertile pinnules or are specialized for vegetative propagation. The latter functioned as the foliar equivalent of stolons. While some characters of the B. tridentata plant are similar to those of Botryopteris forensis, generitype of the Botryopteridaceae, others are more comparable to those of Psalixochlaena cylindrica, generitype of Psalixochlaenaceae, suggesting the need for reevaluation of systematic relationships among species of the Botryopteridaceae and Psalixochlaenaceae.     

Rhacophyton from the Upper Devonian of West Virginia

A new species of Rhacophyton, R. ceratangium , is described from Upper Devonian rocks of West Virginia, U.S.A.; this is synonymous with R. incertum (Dawson) Krausel and Weyland but reasons are cited to indicate that the latter species name is not appropriate.
The collections include: stems up to 2 cm in diameter bearing bipinnate, non-laminate vegetative fronds; abundant well preserved fertile fronds that show clearly the distinctive morphology of their sterile and fertile pinnae; fragments of axes with woody tissues petrified.
The sporangia are particularly distinctive with their long slender tip; they dehisced longitudinally and contained several hundred spores; all available evidence indicates that the plant was homosporous. All petrified axes have a slender bar-shaped strand of primary wood swollen at either end and surrounded by strongly developed secondary wood consisting of scalariform tracheids and rays.
R. ceratangium is closely related to the Belgian R. zygopteroides Leelercq. A comparison with other Devonian and Carboniferous pteridophytes suggests that Rhacophyton is probably a primitive member of the Progymnospermopsida or immediately ancestral to that group.     

中国东北古新世乌云植物群: Woodwardia bureiensis, Dryopteris sp.和 Osmunda sachalinensis

在黑龙江省嘉荫县乌云镇古新世乌云植物群中新发现的Woodwardia bureiensis, Dryopteris sp. 和 Osmunda sachalinensis在中国也是新记录。Woodwardia bureiensis Fedotov与其他种的主要区别是小羽片排列紧密且边缘彼此靠合。Osmunda sachalinensis小羽片基部宽楔, 而以前乌云植物群所报道的Osmunda greenlandica小羽片基部平展。     

广西蕨类植物新记录科——光叶藤蕨科

报道了广西蕨类植物一新记录科——光叶藤蕨科.该科植物以茎圆柱形攀缘;叶二型,通常为奇数羽状;侧生羽片以关节着生于叶轴;不育叶羽片边缘具软骨质硬齿,羽片基部上侧具一腺体;叶脉细密,中肋两侧各具1行窄长网眼,向外伸出分离小脉;能育叶线形,孢子囊群密被羽片下面,无隔丝而与其他蕨类物种相区分.目前该科在广西仅记录光叶藤蕨1种,...     

STENOKOLEOS BIFIDUS SP. N. IN THE UPPER DEVONIAN OF NEW YORK STATE

Stenokoleos is a genus for petrified axes from the Mississippian New Albany Shale to which an Upper Devonian occurrence in New York is added. Two orders of branching were known and the plant was thought to be related to coenopterid ferns. The new petrified axes from New York reveal three orders of branching. A pair of rachides emerges from one side of the stem at each node. Their position alternates at successive nodes (distichous). Each rachis bears alternately arranged pinnae. The shape of the xylem strand and the number of protoxylem areas are variable. Traces to the pairs of rachides arise either as two separate strands or as a single strand that is presumed to divide while still within the cortex of the stem. Traces to pinnae are ellipsoid or clepsydroid. Tracheids are scalariform and uni- or biseriate, circular-bordered pitted. Peripheral loops are present in all orders of branches. Protoxylem strands are numerous and maturation is mesarch. Cortex is parenchymatous where it is preserved but outer cortex is missing. Stenokoleos and Reimanniopsis are placed in a new family, Stenokoleaceae. This is classified as Incertae Sedis among Pterophytina in Tracheophyta. It is suggested that the plant is related more closely to the Mississippian pteridosperms Tristichia and Tetrastichia than to the coenopterid ferns.     

Osmunda (Osmundaceae) from the Triassic of Antarctica: an example of evolutionary stasis

Compressed specimens of the fern Osmunda are described from the Triassic of the Allan Hills, Antarctica. The specimens consist of a once pinnate, deeply pinnatifid fertile frond as well as several sterile specimens. Six pinnae are present on the partial fertile rachis, with two sterile pinnae above four fertile pinnae. Both sterile and fertile specimens are virtually identical to the modern species Osmunda claytoniana. Entire fronds are fragmentary; the longest is 21 cm in length. Sterile pinnae are alternate and deeply pinnatifid, with slightly toothed pinnules and dichotomous venation. Fertile pinnae are 1-1.3 cm long, once pinnate, and lack vegetative lamina. Sporangia are clustered, each 300-375 um in diameter, and possess a transverse annulus 6-8 cells long; dehiscence is by a vertical slit. Fronds arise from a rhizome 4 cm long by 1 cm wide; two croziers are present on the rhizome. Two frond segments up to 6 cm long and three deeply pinnatifid pinnae are present on the uppermost part of one rachis. Pinnules are ~4 mm long and 2-3 mm wide. The presence of this Osmunda species in the Triassic demonstrates stasis of frond morphology, both fertile and vegetative, for the genus.     

On Paleozoic plants from marine strata: Trivena arkansana (Lyginopteridaceae) gen. et sp. nov., a lyginopterid from the Fayetteville Formation (middle Chesterian/Upper Mississippian) of Arkansas, USA

Five permineralized seed fern stems from the Fayetteville Formation (middle Chesterian/Upper Mississippian) of Arkansas conform to the concept of lyginopterid seed ferns. However, these specimens are unlike all previously reported lyginopterids, and the name Trivena arkansana (Lyginopteridaceae) gen. et sp. nov. is proposed. The stems are up to 30 by 19 mm in diameter and have pentagonal pith and eustele of five cryptic sympodia. Secondary tissues include abundant xylem with numerous wide rays and phloem surrounded by a periderm. The cortex is parenchymatous with abundant sclerotic clusters: some clusters are randomly dispersed and some are in discontinuous rows. Sclerenchyma bands form the "Dictyoxylon"-type outer cortex. Leaf traces diverge in a 2/5 phyllotaxy. Traces, accompanied by concentric secondary xylem, increase in size as they extend through the secondary xylem of the stem. The trace assumes a squat C shape at the outer margin of the secondary xylem and in the cortex divides into three discrete bundles, each surrounded by secondary xylem. Galleries within the phloem contain arthropod coprolites and exhibit wound response, suggesting plant-arthropod coevolution. The discovery of this new lyginopterid stem adds to the growing list of unique taxa described from the Fayetteville Formation and further solidifies its reputation as one of the most important Upper Mississippian plant fossil sites in North America.     

Root distributions and elemental accumulations of Chinese brake (Pteris vittata L.) from As-contaminated soils

A field investigation was conducted to understand the root distributions and elemental accumulations of Chinese brake (Pteris vittata L.), an As-hyperaccumulator, grown in soils with a gradient of As concentration near an arsenic sulphide mine. The root distribution was affected not only by the levels of soil As, but also by soil texture. Plants grew better in sandy loam soils than in clay soils. Increases in the ratio of frond biomass to underground biomass were correlated with decreasing soil As concentration. Root densities of the plant decreased from 0–10 cm, 10–20 cm to 20–30 cm in the soil profiles. Most of the roots were concentrated in the upper 0–10 cm layer. Under high As conditions, As concentrations in different tissues followed the trends: pinnae > rhizomes ≈ roots of 0–10 cm > roots of 10–20 cm > roots of 20–30 cm > petioles, however, As concentrations in pinnae were higher than those in rhizomes under low As conditions. The rhizomes and pinnae were the main As pools, storing 75–86% of the total As uptaken by the plants. The rhizome, a `buffer-storage' for plant As, maintained high concentrations of As under high soil As while the pinnae became the most important organ of storing the As under low soil As. Chinese brake might possess the ability of adjusting its As-storage under different soil As levels. The plant can not only hyperaccumulate As from the soils, but also enriched P and Ni from the soils and translocated them to the fronds. It is important to improve the root distribution for phytoremediation of As-contaminated soils using Chinese brake.     

Sector analysis and predictive modelling reveal iterative shoot-like development in fern fronds

Plants colonized the terrestrial environment over 450 million years ago. Since then, shoot architecture has evolved in response to changing environmental conditions. Our current understanding of the innovations that altered shoot morphology is underpinned by developmental studies in a number of plant groups. However, the least is known about mechanisms that operate in ferns--a key group for understanding the evolution of plant development. Using a novel combination of sector analysis, conditional probability modelling methods and histology, we show that shoots, fronds ('leaves') and pinnae ('leaflets') of the fern Nephrolepis exaltata all develop from single apical initial cells. Shoot initials cleave on three faces to produce a pool of cells from which individual frond apical initials are sequentially specified. Frond initials then cleave in two planes to produce a series of lateral merophyte initials that each contributes a unit of three pinnae to half of the mediolateral frond axis. Notably, this iterative pattern in both shoots and fronds is similar to the developmental process that operates in shoots of other plant groups. Pinnae initials first cleave in two planes to generate lateral marginal initials. The apical and marginal initials then divide in three planes to coordinately generate the determinate pinna. These findings impact both on our understanding of fundamental plant developmental processes and on our perspective of how shoot systems evolved.     

Ontogeny and ecology of the filicalean fern Oligocarpia gothanii (Gleicheniaceae) from the Middle Permian of China

Reinvestigation of Oligocarpia gothanii Halle (Gleicheniaceae) from the Permian Period of China has uncovered a rare demonstration of ontogenetic succession in numerous intact plants and has led to emendation of the diagnosis and typification of the species. Reconstruction of the fern's vegetative life cycle shows a small rosette-shaped juvenile plant with immature fronds of pinnae undifferentiated into pinnules. The second stage is a series of leafy shoots increasing in size and complexity and bearing fronds essentially comparable with those of the adult plants. Mature plants have sphenopteroid-type fronds differentiated into vegetative and fertile fronds. Close association of plants on the same bedding plane and the presence of a connecting root network between shoots, show that juvenile plants spread by vegetative propagation using underground stolons. Sedimentological information and co-occurrence with the bryophyte Thallites hallei Lundblad suggests that O. gothanii occupied a wetland habitat and was preserved in an obrution event consistent with flooding of marginal areas in a fluvio-deltaic setting. Although recent studies on Oligocarpia have focused exclusively on reproductive features, new ontogenetic information suggests that plants growing in rapidly changing environments may have been reliant on vegetative propagation and would not have needed to reach sexual maturity for successful reproduction.     

New reconstruction of Weichselia reticulata (Stokes et Webb) Fontaine in Ward emend. Alvin, 1971 based on fertile remains from the middle Albian of Spain

Exceptionally well-preserved specimens from the middle Albian of Spain corresponding to a nearly complete fertile frond and fragments of pinnae containing soral clusters of the tree fern Weichselia reticulata have provided new data about the structure and arrangement of pinnae and their associated fertile reproductive structure. This new material has been compared with the previous studies, and recostructions of this fern and the new data indicate the segregation of vegetative and fertile fronds within the main stipe of this fern.     

秦岭地区石炭纪两种新的扇状脉植物

记述的两种新植物分别来自秦岭地区的凤县和镇安县。产于凤县草凉驿红花铺草凉驿组的Adiantites honghuapuensis sp．nov．,至少二次羽状复叶,羽片线形,以宽角着生于羽轴上;小羽片椭圆形,羽片基部的小羽片偶尔分裂为2—3个裂片。小羽片基部收缩,有短柄或以较宽的基部着生于羽轴上,扇状脉。另一产自镇安县茅坪东山梁二峪河组的Qinlingopteris orientalis gen．et sp．nov．,其特征是二次羽状复叶,末二级羽轴与末级羽轴夹角较小,大约30^#左右。小羽片亚对生,长卵形或亚圆形,顶端较窄,中部较宽,基部较狭并具短柄;叶脉扇状;羽轴上具间小羽片,间小羽片与正常小羽片等形同大。草凉驿组的地质时代大致为纳缪尔期至维斯发早期,而二峪河组则为早石炭世维宪期。     

A new species of Polystichum (Pteridophyta: Dryopteridaceae) from South Africa

A new Polystichum (Pteridophyta: Dryopteridaceae) species, P. incongruum J.P.Roux sp. nov. from the Western and Eastern Cape Provinces from Soudi Africa is described. This variable species is related to P. pungens (Kaulf.) C.Presl but differs from it in pinnule morphology, the frequent occurrence of glandular cells along the sporangium stalk, the (more rare) occurrence of clavate unicellular glands along the indusium margin and a chromosome number of 2 n = 164.     

Taonia lacheana sp. nov. (Dictyotales, Phaeophyta), from the Mediterranean Sea

A new species of the genus Taonia (Dictyotales, Phaeophyta) is described from the Mediterranean Sea. The species is characterized by pseudodichotomous fronds having entire margins and by a pronounced differentiation between the medullary and cortical cells throughout the thallus. Only tetrasporangial plants were found. The species differs from T. atomaria f. ciliata in having differently sized cells in cross section and an entire margin and from T. lennebackerae in both the habit and in the shape of cells in longitudinal section.     

Dicksonites pluckenetii(Schlotheim) Sterzel and its affinity with Callistophytales

Female and male (?) fronds of the Stephanian Dicksonites pluckenetii(Schl.) Sterz. initially described by Grand'Eury (1905) have been reinvestigated. Seeds were attached abaxially and subapically to strongly reduced linear pinnules of pinnae which are otherwise similar to sterile ones. Associated synangia are of the Pterispermostrobus type. They appear to have occupied marginal or submarginal position on modified pinnules of irregular outlines. The affiliation of D. pluckenetii with the order Callistophytales is supported. Considering that the oldest (Westphalian) members of D. pluckenetii had unmodified seed-bearing fronds, the progressive reduction of fertile fronds in the evolution of the Callistophytales is suggested. Further stages of the process are observed in the Permian family Trichopityaceae (order Peltaspermales). In another lineage of the Callistophytales the fertile fronds were planated and leafless.     

A contribution to the knowledge of the pteridosperm genera Pseudomariopteris Danzé-Corsin nov. emend. and Helenopteris nov. gen

The macromorphology and epidermal anatomy of three Late Carboniferous-Early Permian pteridosperm species, conventionally assigned to the form-genus Pseudomariopteris Danzé-Corsin, are described from the Stephanian of the Blanzy-Montceau Basin (Central France). The generic diagnosis of Pseudomariopteris is emended, and P. busquetii is designated as the type species of the genus. The combination P. cordato-ovata (Weiss) Gillespie et al. is validated to replace the illegitimate name P. ribeyronii (Zeiller) Danzé-Corsin. The species diagnoses of P. busquetii and P. cordato-ovata are emended. On the basis of its epidermal anatomy, P. paleaui, another species orininally described from Central France, is transferred to the newly established genus Helenopteris Krings et Kerp, and the new combination Helenopteris paleaui is introduced. Lectotypes of P. busquetii and H. paleaui are selected. In addition, specimens from other basins are (re-)examined and illustrated. Seeds attached to a P. busquetii specimen suggest a callistophytalean relationship for Pseudomariopteris. Compression fossils and cuticles of Pseudomariopteris and Helenopteris are interpreted in terms of palaeoecology: Pseudomariopteris busquetii and P. cordato-ovata had climbing/scrambling growth habits; specialized climber hooks can be demonstrated for both species, either in compression or in cuticular preservation. Although the growth habit of H. paleaui is not yet entirely clear, the size of its fronds suggests that this taxon most probably was also a scrambler/climber. Finally, based on epidermal features, a tentative reconstruction of stages of the pinnule ontogeny of H. paleaui is provided.     

The role of Hydropteris pinnata gen. et sp. nov. in reconstructing the cladistics of heterosporous ferns

Large segments of intact plants that represent a heterosporous fern have been discovered within an aquatic plant community from the Late Cretaceous St. Mary River Formation near Cardston in southern Alberta, Canada. Branching rhizomes of Hydropteris pinnata gen. et sp. nov. are 1–2 mm wide. They produce fronds at intervals of 2–12 mm and bear numerous elongated roots. Fronds, up to approximately 6 cm long, are pinnate with subopposite to alternate pinnae that exhibit anastomosing venation. Large, multisoral sporocarps occur at the junctures of the rhizome and frond rachides. Both microsporangiate massulae and megaspore complexes occur within each sporocarp. Megaspore complexes are assignable to the sporae dispersae genus Parazolla Hall. Microspores are trilete, smooth-walled, and are embedded in episporal material of the massulae. A numerical cladistic analysis indicates that the heterosporous aquatic ferns are monophyletic, and not as closely related to either schizaeaceous or hymenophyllaceous ferns as they are to some other filicaleans. Systematic revisions are proposed to reflect newly recognized cladistic relationships within the heterosporous clade, and character originations in the evolution of heterosporous aquatic ferns are evaluated. Hydropteridaceae fam. nov. is proposed, and included with Salviniaceae and Azollaceae in the Hydropteridineae subord. nov., and the Hydropteridales Willdenow.     

Reiterative growth in the complex adaptive architecture of the Paleozoic (Pennsylvanian) filicalean fern Kaplanopteris clavata

Reiteration is a widespread component of plant growth whose evolutionary importance in ferns is not recognized widely. We introduce and discuss the growth architecture of Kaplanopteris clavata, a fossil filicalean fern from the Pennsylvanian (ca. 305 million yeas old), focusing on types of reiteration exhibited by this species and on the adaptive and phylogenetic significance of reiteration for ferns in general. Kaplanopteris clavata combines two types of reiterative growth where growth modules are borne on fronds: (1) entire fronds derived from primary pinnae, and (2) epiphyllous plantlets. This combination of reiterative pathways, unique among fossil and living ferns, allowed K. clavata to explore ecospace through an opportunistic combination of scrambling, climbing and epiphytic growth. Kaplanopteris clavata underscores the organographic importance of fronds (as opposed to stems) in the adaptive architecture of ferns, emphasizing functional convergences between the different Baupla̋ne of ferns and angiosperms. This unique combination of reiterative pathways is interpreted as a derived condition illustrating the structural and developmental complexity achieved by some filicaleans during the first major evolutionary radiation of leptosporangiate ferns.     

Sanio's laws revisited. Size-dependent changes in the xylem architecture of trees

Early observations led Sanio [ Wissen. Bot. , 8 , (1872) 401] to state that xylem conduit diameters and lengths in a coniferous tree increase from the apex down to a height below which they begin to decrease towards the tree base. Sanio's law of vertical tapering has been repeatedly tested with contradictory results and the debate over the scaling of conduit diameters with distance from the apex has not been settled. The debate has recently acquired new vigour, as an accurate knowledge of the vertical changes in wood anatomy has been shown to be crucial to scaling metabolic properties to plant and ecosystem levels. Contrary to Sanio's hypothesis, a well known model (MST, metabolic scaling theory) assumes that xylem conduits monotonically increase in diameter with distance from the apex following a power law. This has been proposed to explain the three-fourth power scaling between size and metabolism seen across plants. Here, we (i) summarized available data on conduit tapering in trees and (ii) propose a new numerical model that could explain the observed patterns. Data from 101 datasets grouped into 48 independent profiles supported the notions that phylogenetic group (angiosperms versus gymnosperms) and tree size strongly affected the vertical tapering of conduit diameter. For both angiosperms and gymnosperms, within-tree tapering also varied with distance from the apex. The model (based on the concept that optimal conduit tapering occurs when the difference between photosynthetic gains and wall construction costs is maximal) successfully predicted all three major empirical patterns. Our results are consistent with Sanio's law only for large trees and reject the MST assumptions that vertical tapering in conduit diameter is universal and independent of rank number.