Ectophloic Siphonostele Research Articles

A new anatomically preserved osmundalean stem Tiania resinus sp. nov. from the Lopingian (upper Permian) of eastern Yunnan, China

This paper describes an osmundalean stem from the Lopingian (upper Permian) Xuanwei Formation in eastern Yunnan Province, southwestern China. The stem of T. resinus sp. nov. is very small, only ca. 1 cm in diameter, and is characterised by the bi-zoned pith, pith cells typically vertically elongated, ectophloic siphonostele, primary xylem mesarch and 6–8 tracheid thick, a mass of sclerenchymatous cells in the adaxial concavity of the leaf trace and an arch-shaped secretory cell band surrounding the adaxial side of the leaf trace. The stem is compared with the member of Osmundales and is assigned into the genus Tiania of the extinct family Guaireaceae, where it represents the smallest member of the Guiariaceae. Distinctions from Tiania yunnanense include no sclerenchymatous and secretory cells in the primary xylem and the secretory cells in the cortex distributing around the adaxial side of the leaf trace and lead to the establishment of Tiania resinus sp. nov. T. resinus together with the three other species from three genera osmundalean trunk/stem have now been reported from the Upper Permian of eastern Yunnan and western Guizhou, southwestern China. Discovery of the new species enriches the diversity of osmundalean plants from the Cathaysian Flora and offers evidence that the area of eastern Yunnan and western Guizhou may be an centre for the distribution and the early evolution of extinct osmundalean family Guaireaceae.

Tiania yunnanense gen. et sp. nov., an osmundalean stem from the Upper Permian of southwestern China previously placed within Palaeosmunda

The Permian aged osmundalean fern Palaeosmunda yunnanense Tian et Chang has been re-investigated based on the original specimens and demonstrated to represent a new genus within the extinct family Guaireaceae that we name Tiania yunnanense (Tian et Chang) gen. et. comb. nov. The stem of T. yunnanense is small, c. 30mm in diameter, and comprises an ectophloic siphonostele without leaf gaps. Pith is bilayered and consists of longitudinally elongated cells. Cortex is not differentiated into an inner parenchymatous and outer sclerenchymatous zone characteristic of members of the Osmundaceae, and possesses longitudinally elongated cells and large secretory cells. Leaf traces are numerous (>100) and adaxially curved, with two endarch protoxylem strands upon departing the stele, increasing to more than four protoxylem strands as the trace passes the cortex, all distributed along the adaxial side of the leaf trace. Leaf traces have more-or-less incurved lateral tips, and are encircled by a vascular bundle sheath. A mass of thick-walled, longitudinally elongated cells occur in the adaxial concavity of the leaf trace. Adventitious roots arise singly from the abaxial and lateral margin of individual departing leaf traces, and extend in a sinuous manner horizontally and longitudinally. Abundant tyloses-like contents occur in cells of the cortex and represent the first account of these within fossil Osmundales, but unlike other plant groups in which they occur within xylem, fibre-tracheids and lactifers, in T. yunnanense they occur in longitudinally elongated cortex cells where they presumably impeded fungal hyphae growth. Radially aligned ‘secondary’ parenchyma within the stem appears to represent a wound reaction in the cortex in the living plant. Due to its siphonostele without leaf gaps, Tiania is interpreted as an evolutionary intermediate between the protostelic thamnopterids and the more advanced dictyostelic osmundaleans. Biogeographic implications of Tiania are discussed from which it is concluded that the osmundalean diversity from the Late Permian of South China is unusually high and that these plants are likely to play an increasingly important role in our understanding of the early evolutionary history and systematic relationships of the Osmundales.

A new species of Millerocaulis (Osmundaceae, Filicales) from the Middle Jurassic of China

A new species, Millerocaulis sinica, is established based on a specimen collected from Lanqi Formation (Middle Jurassic) near Changgao Town, Liaoning Province of China. The specimen represents a stem surrounded by a mantle of stipular petiole bases and adventitious roots. The stem, 11×12 mm in diameter, consists of ectophloic siphonostele with rare complete leaf gaps and a two-layered cortex containing 31–35 leaf traces. The pith consists of homogeneous parenchyma. The outer cortex is composed of sclerenchyma, and is thicker than the parenchymatous inner cortex. When departing from the stem, the leaf traces are flattened C-shaped, with an endarch protoxylem which bifurcates at the base of petiole. Sclerenchyma rings are heterogeneous. A crescent-shaped sclerenchymatous mass occurs in the concavity of petiolar vascular strands. A large sclerenchymatous mass and several small sclerenchymatous strands are aligned in each stipular expansion at the periphery of the specimen. M. sinica, which has thick band occupying abaxial semicircle of sclerenchyma rings as well as a heterogeneous sclerenchyma mass and several sclerenchyma strands scattered in the stipular expansions, is much closer to these of subgenus Osmunda than subgenus Plenasium and subgenus Osmundastrum in the genus Osmunda. Therefore, it is suggested that there is a possible phylogenetic relationship between M. sinica and subgenus Osmunda.

An anatomically preserved arborescent lycopsid, Sublepidodendron songziense (Sublepidodendraceae), from the Late Devonian of Hubei, China

Sublepidodendron is a common megafossil plant in the Late Devonian of China, but historically the generic delimitation based on leaf bases masked its true systematic position. A reinvestigation of S. songziense from the Late Devonian Hsiehchingssu Formation, Hubei, China, provides new insights into its internal anatomy and reproductive morphology. This arborescent lycopsid is characterized by small, vertically elongated leaf bases arranged in spirals, presence of false leaf scars, possibly bearing separate cones, and association with a stigmarian rhizomorph. The potential for organic connections of these detached organ genera has been noted for other Sublepidodendron species. The anatomy of S. songziense axes from two levels reveals that the thinner axis may bear an ectophloic siphonostele with a filamentous pith and an outer cortex. The thicker axis has a siphonostele with a branch gap, two-zoned pith with secondary thickenings, multiseriate rays across secondary xylem, a thick periderm, and primary and secondary tracheid walls characterized by "Williamson's striations." Similarities to synapomorphies of Diaphorodendraceae and Lepidodendraceae suggest that S. songziense bears a closer affinity to Lepidodendrales rather than Protolepidodendrales, as formerly thought. Widespread occurrence of Sublepidodendron implies that phylogenetically advanced arborescent lycopsids must have diverged by the Late Devonian.

A New Species of Millerocaulis (Osmundaceae) from the Lower Cretaceous of California.

A small permineralized osmundaceous stem has been collected from marine sediments of the Early Cretaceous (Aptian), Upper Chickabally Member of the Budden Canyon Formation near Ono, California. The specimen, 8.5 cm long and 5.4 cm wide, represents a stem surrounded by a mantle of stipular leaf bases and adventitious roots. A large number of sections were studied through the use of the cellulose acetate peel technique. The stem was erect, 11x13 mm in diameter, with a parenchymatous pith and two-layered cortex. The stele is an ectophloic siphonostele with 65-79 leaf traces in the stem per cross section. Leaf gaps are only produced in 13% of the departing traces. Most leaf traces have "delayed" gaps or completely lack leaf gaps. Leaf traces are C-shaped, endarch, with one protoxylem strand, and have sclerenchyma lining the adaxial concavity. Leaf bases have stipular wings with large patches of heterogeneous sclerenchyma and a few scattered strands outside of the heterogeneous sclerotic ring. Patches of sclerenchyma occur inside the ring and outside of the vascular tissues. Numerous diarch roots arise singly or doubly from the leaf traces as they depart the axis stele. Although the stem compares fairly closely to both Ashicaulis Tidwell and Millerocaulis Erasmus ex Tidwell emend. Tidwell, it is most similar to Millerocaulis. However, the combination of characters observed in our specimen differs from that of the seven known species of Millerocaulis. This stem is described as Millerocaulis embreei sp. nov. and is the youngest known species of the genus and the first to be found in the Northern Hemisphere.

The pteridophyte Ashicaulis livingstonensis (Osmundaceae) from the Upper Cretaceous of Williams Point, Livingston Island, Antarctica

The presence of Ashicaulis livingstonensis sp. nov. in the Upper Cretaceous Williams Point Beds of Livingston Island, Antarctica, represents an important new record of the Osmundaceae in the southern high latitudes. It extends the range of Ashicaulis to the Late Cretaceous. Ashicaulis livingstonensis sp. nov. comprises a small stem surrounded by a mantle of petiole bases and roots. Leaf gaps are narrow, rapidly closing, or occasionally incomplete, and the stem is best regarded as ectophloic siphonostele. The anatomy of Ashicaulis livingstonensis suggests an erect, probably mound‐forming fern.

Vascular Anatomy of the Subterranean Organ of Ophioglossum vulgatum L.

The vascular anatomy of subterranean rhizome and root of Ophioglossum vulgatum was studied. The vascular cylinder of the rhizome which had developed adventitiously is ectophloic siphonostele with endarch primary xylem maturation. In the basal part of the rhizome ectophloic siphonostele reveals a complete cylinder of vascular tissue, whereas an ectophloic siphonostele with overlapping gaps occurs in the upper part of the rhizome. Each meristele is arranged as collateral bundle. The bulk of primary xylary elements in the vascular bundles is radially aligned. The roots are monarch with exarch xylem maturation and the monarch vascular pattern reveals opposite arrangement of xylem and phloem. The relation between stelar and total root diameter shows a low correlation. No signs of secondary thickening are found either in the rhizomes or the monarch roots. The comparison of anatomical features of vascular system of the rhizome and root with other ferns shows significant differences.

Schaffneria nigripes (Aspleniaceae): morfogénesis del gametofito y anatomía y morfológía del esporofito

Se aportan datos de la morfología y la anatomía del esporofito y del desarrollo del talo gametofito de Schaffneria nigripes Fée (Aspleniaceae ); las hojas son enteras y romboides a obovadas, con estomas solamente en la cara abaxial; el mesófilo es un parénquima esponjoso sin parénquima compacto; la estela, con una endodermis bien definida, es una sifonostela ectofloica. Las esporas tienen viabilidad larga y su germinación es del tipo Vittaria; los gametofitos maduros son cordiformes irregulares, con pelos no glandulares en ambas superficies y en los márgenes.

Millerocaulis richmondii sp. nov., an osmundaceous fern from Mesozoic strata near Little Swanport, Tasmania, Australia

A permineralised rhizome from Mesozoic strata south of Little Swanport, Tasmania, represents a new species of Millerocaulis (M. richmondii).Its stem is 6 x 7 mm across and is surrounded by adhering leaf bases with each having a stipular expansion typical of the Osmundaceae. The xylem of the ectophloic siphonostele comprising this stem is dissected by leaf gaps and consists of 14 xylem strands in its cylinder.Twenty leaf traces occur in a transverse section of its cortices. The xylem of its leaf traces and petiolar vascular strands is generally curved adaxially with a single protoxylem cluster being median on the trace. This proroxylem cluster bifurcates into two protoxylem groups immediately after leaving the stem and upon entering the petiole. The sclerotic ring of the petiole base is uniform in width and cell-wall thickness. A mass of sclerenchyma present in the adaxial concavity of the petiolar vascular strand expands at higher levels of the petiole until it fills the concavity of the strand and becomes immediately adjacent to the sclerotic ring. A large, round cellular mass of sclerenchyma occurs in the stipular expansions midway between their sclerotic rings and their tips. Millerocaulis richmondii is an additional species in the family Osmundaceae which was very abundant in Tasmania during mid-Mesozoic time.

Grammatocaulis donponii gen. et sp. nov., a permineralized fern from the Jurassic of Queensland, Australia

A permineralized fern stem from Middle to Late Jurassic sediments (Injune Creek Group) in the Wandoan area of southeastern Queensland is assigned to the new genus and species Grammatocaulis donpanii. The stem possesses an ectophloic siphonostele with the xylem divided into an outer zone of long tracheids and an inner zone of short, wide, parenchyma-like tracheids surrounding a pith. Leaf traces are round in cross section in the parenchymatous inner cortex, becoming linear to oblong in the outer cortex and outside of the stem. Petiole bases have sclerotic rings around vascular strands, but lack stipular wings. Some of its outermost petiolar vascular strands assume a C-shape which may be due to distortion. Parenchymatous tissue occurs in the middle of the protoxylem at the ends of the elliptical petiolar vascular strands. At higher levels, the parenchymatous tissue of the strands is found in the metaxylem as well. Nonglandular multicellular scales occur on the petioles. Although the family of this genus is unknown, it is similar anatomically to Grammatopteris of the Anachoropteridaceae from the Late Paleozoic of Europe. If these two genera are related, this specimen suggests more structural diversity, a wider geographic distribution and a longer geologic range for the Anachoropteridaceae than previously known.

New fern stems from the Triassic of Antarctica

Five new genera of filicalean fern stems are described from Antarctic silicified permineralizations of early Middle Triassic age. Antarctipteris gen. n. stems are rhizomatous, 5–15 mm in diameter and possess an exarch protostele. Leaf traces are initially bar-shaped and become C- or V- shaped in the petiole. The stele and leaf traces are surrounded by cortical sclerenchyma strands. Fremouwa gen. n. is a creeping rhizome 1–4 mm in diameter which possesses an endarch, ectophloic siphonostele. C-shaped leaf traces are produced radially and migrate through the cortex obliquely. Schleporia gen. n. stems are 3–4 mm in diameter and possess a mesarch ectophloic siphonostele. Branching occurs by initiation of two C-shaped xylem strands that fuse adaxially and then abaxially to form a cylinder. Leaf traces are C-shaped and distantly spaced. Schopfiopteris gen. n. is a creeping rhizome 1.5–11 mm in diameter which possesses an endarch, ectophloic siphonostele. Stems produce C-shaped leaf traces on one side of the stele. Soloropteris gen. n. stems are cylindrical, 1–4 mm in diameter, and possess a mesarch amphiphloic siphonostele which produces C-shaped leaf traces. Lateral buds are axillary or adaxial to the widely spaced leaves. The stems are compared anatomically to Paleozoic filicalean ferns and an attempt is made to suggest relationships to extant families within the Filicales.

OSMUNDA WEHRII, A NEW SPECIES BASED ON PETRIFIED RHIZOMES FROM THE MIOCENE OF WASHINGTON

Silicified rhizomes from Miocene strata near Yakima, Washington represent a new species of Osmunda. The stems are 8–13 mm in diameter and are surrounded by a thick sheath of adherent leaf bases, each of which shows stipular expansions typical of the Osmundaceae. The new species has an ectophloic siphonostele in which the xylem cylinder is dissected by leaf gaps with 12–14 strands being visible in a given stem cross section. Such sections also show 12–16 leaf traces in the cortex. The xylem of each leaf trace diverges from the xylem cylinder of the stem as an adaxially concave strand with its protoxylem organized into a single medial adaxial cluster. Initial bifurcation of the leaf‐trace protexylem occurs as the leaf trace passes through the outer cortex of the stem. In the basal part of the stipular region of the petiole base, thick‐walled fibers form an arch on the abaxial side of the sclerenchyma ring around the petiolar bundle. This arch persists throughout most of the length of the stipular region, with the thick‐walled fibers becoming reorganized into two lateral masses in the distal part of the stipular region. Similar thick‐walled fibers form an elongate strip of tissue in each wing of the stipule along with several small clusters scattered near the sclerenchyma ring. The new species belongs to the subgenus Osmunda and shows that during the Neogene, the latter existed as a group of closely related species much as it does today. Furthermore, Osmunda wehrii combines features of the modern O. regalis, O. japonica, and O. lancea with those of O. claytoniana and thus supports the inclusion of the latter species in the subgenus Osmunda.

Stem Anatomy and Phyllotaxis in Ophioglossum petiolatum

Besides Ophioglossum petiolatum Hooker, subg. Ophioglossum includes approximately 20 other species. All are characterized by a radially erect, underground stem which bears a simple, oval or lanceolate leaf blade at the base of which arises a sporangia-bearing segment (Campbell, 1911, p. 86; Claussen, 1938, pp. 111-112, 1954). Stem anatomy of only seven species has been described: 0. vulgatum (Rostowzew, 1891; Vasisht, 1927), 0. moluccanum (Campbell, 1911), 0. aitchisonii (Vasisht, 1927), 0. fibrosum (Maheshwari & Singh, 1934), 0. littorale (Nozu, 1956), 0. lusitanicum (Gewirtz & Fahn, 1960), and 0. reticulatum (Sen, 1968). At the base of the stem is a protostele surrounded either partially or completely by phloem. Above this point pith develops, and the stele is an ectophloic siphonostele. The remainder of the stem contains a dictyostele of anastomosing collateral bundles with endarch xylem and no secondary vascular tissues. Root bundles are attached at the meristele edges. It is not known whether roots are associated consistently with leaf bases. Rostowzew found one root attached near each leaf base in 0. vulgatum, and Vasisht found the same condition in 0. aitchisonii. It seems possible that the roots of some species bear no discernible relation to the leaf bases; figure 2 of Gewirtz and Fahn may be interpreted as indicating this.

The Lepidophytic Affinities of the Genus Chinlea and Osmundites walkeri

Chinlea campii Daugherty and Osmundites walkeri Daugherty are species of petrified stems from the Upper Triassic Chinle Formation of Arizona that were described as members of the fern family Osmundaceae. Investigation of additional material indicates that the two species are conspecific and belong to the Lepidophyta. The stems are radially symmetric and have an ectophloic siphonostele in which the xylem cylinder is thick and deeply furrowed. Internal pressure against the xylem cylinder caused by the lateral expansion of the pith in some stems produces what appears in transverse section to be a ring of up to 60 separate xylem strands. Leaf traces are small, terete, collateral and have exarch xylem. They are arranged in a tight spiral. Adventitious roots, secondary xylem, and secondary cortex are lacking. The stems are classified under the binomial Chinlea campii, and other axes that have similar cortical anatomy but in which all vascular tissues have decayed are treated as Chinlea sp. Both types of stems are interpreted as ephemeral aerial shoots of an herbaceous plant. Of the known fossil Lepidophyta, Chinlea is most similar to Pleuromeia and Nathorstiana, but it differs from each of these genera in a number of respects and is therefore included in Lepidophyta incertae sedis.

THE LEPIDOPHYTIC AFFINITIES OF THE GENUS CHINLEA AND OSMUNDITES WALKERI

Chinlea campii Daugherty and Osmundites walkeri Daugherty are species of petrified stems from the Upper Triassic Chinle Formation of Arizona that were described as members of the fern family Osmundaceae. Investigation of additional material indicates that the two species are conspecific and belong to the Lepidophyta. The stems are radially symmetric and have an ectophloic siphonostele in which the xylem cylinder is thick and deeply furrowed. Internal pressure against the xylem cylinder caused by the lateral expansion of the pith in some stems produces what appears in transverse section to be a ring of up to 60 separate xylem strands. Leaf traces are small, terete, collateral and have exarch xylem. They are arranged in a tight spiral. Adventitious roots, secondary xylem, and secondary cortex are lacking. The stems are classified under the binomial Chinlea campii, and other axes that have similar cortical anatomy but in which all vascular tissues have decayed are treated as Chinlea sp. Both types of stems are interpreted as ephemeral aerial shoots of an herbaceous plant. Of the known fossil Lepidophyta, Chinlea is most similar to Pleuromeia and Nathorstiana, but it differs from each of these genera in a number of respects and is therefore included in Lepidophyta incertae sedis.

The Anatomy of Ophioglossum pendulum

1. The root stele varies from diarch to hexarch. The roots branch monopodially, and the branches are diarch at the base. 2. Buds develop upon the roots in the same manner as in O. vulgatum. 3. The rhizomes are always radial in structure; the leaves are inserted in an irregular spiral. 4. The connection of the stem stele with that of the parent root is very variable; no phylogenetic significance can be attached to the details of development of the stem stele of a bud. 5. The stele of a mature rhizome is an ectophloic siphonostele with large overlapping leaf gaps; there is no secondary thickening. Root gaps usually occur above the points of insertion of root strands. Incidental gaps not related to outgoing strands occur commonly. 6. In a single large rhizome, numerous xylem strands occur within the pith. These arise from the inner surface of the cylinder or as procambium; some of them are concerned in the closure of leaf gaps, and others disappear as procambium or by fusion with the cylinder. They consist of xylem only. 7. The vascular supply of the leaf consists of 3-12 strands, the number varying with the size of the leaf base. These strands form a cylindrical network in the petiole; in the lower portion of the blade, they constitute two series of strands with xylem oppositely directed. The strands with xylem abaxially directed form the vascular supply of the spike.

A Protocorm of Ophioglossum

1. The protocorm is nearly spherical, with a circular pit in the center of the top. This pit extends downward about 0.8 of the diameter of the protocorm, and the apical cell is located at its bottom. 2. The bases of the leaves are attached to the sides of this pit, with the oldest at the top. The functioning leaf is the seventh, and the primordia of six others occur below it. 3. The vascular cylinder is an everted ectophloic siphonostele with endarch xylem. The leaf trace consists of two strands which attach separately to the cylinder. The roots are numerous and outside the cylinder. 4. The apical cell is a triangular pyramid. The segments divide twice longitudinally before a transverse division occurs. The segments enlarge below more rapidly than above, and the eversion of the cylinder results from this. 5. The segments of the apical cell of a rhizome of O. vulgatum divide transversely first; the later divisions are irregular. The upper and lower portions of a segment enlarge uniformly. 6. The vascular t...