Sclerotic Nests Research Articles

Callixylon wendtiisp. nov., a new species of archaeopteridalean progymnosperm from the Late Devonian of Anti-Atlas, Morocco

ABSTRACTArchaeopterid trees were the main components of most Late Devonian forests. Their aerial axes characterised by a eustele with mesarch primary xylem strands, leaf traces departing radially from cauline bundles and secondary xylem tracheids with radial pits arranged in groups, are referred to the genusCallixylonZalessky. The nineteen species ofCallixylondescribed to date from North America, North Africa, Europe, Xinjiang and several parts of Russia range from the late Givetian to the Mississippian. In this paper, we describe a new species ofCallixylonfrom two specimens collected in the Famennian locality of Mader el Mrakib in eastern Anti-Atlas.Callixylon wendtiisp. nov. is characterised by the presence of sclerotic nests in the pith, a new character for the genus. Its wood shows narrow rays of variable height, with unevenly distributed ray tracheids. Small vascular traces crossing the wood within the two innermost growth rings are interpreted as evidence for short-lived leaves. This discovery adds to the diversity of the genusCallixylonin an area of northern Gondwana that may have been favourable to the establishment of a diverse community of archaeopterid trees.

A Late Pennsylvanian coniferopsid forest in growth position, near Socorro, New Mexico, U.S.A.: Tree systematics and palaeoclimatic significance

The systematics and palaeoclimatic significance of silicified tree-stumps found in growth position in the Late Pennsylvanian (Kasimovian) Atrasado Formation, near Socorro, New Mexico, U.S.A. are described. Two taxa are documented. Macdonaldodendron giganticus (3 or 4 stumps) comprises a broad, non-septate pith containing plate-like sclerotic nests, a non-sympodial vasculature of ~30–35 endarch cauline bundles, pycnoxylic secondary xylem characterised by irregular growth interruptions, and leaf traces that pass through multiple seasons of growth. It is interpreted as a large, evergreen walchian conifer tree. Giblingodendron aridus (10 stumps) comprises a non-sympodial vasculature of ~60–100 mesarch cauline bundles, pycnoxylic secondary xylem showing regular growth rings, and leaf traces apparently occluded at the first ring boundary. The abundant new material allows the diagnosis of this species to be emended, with the pith of relatively juvenile Giblingodendron specimens shown to be distinctly septate, a feature that is absent in relatively mature specimens. The systematic position of this small, deciduous coniferopsid, which bore profuse leaves directly on the stem, remains uncertain. It shares characteristics with dicranophylls, voltzian conifers, cordaitaleans and other enigmatic coniferopsids. The trees are rooted in, and entombed by, microbial carbonates associated with primary gypsum, suggestive of a sabkha environment formed under semi-arid coastal conditions. In contrast, the stumps show subtle growth rings or growth interruptions, which indicate more sub-humid tropical conditions characterised by erratic wet–dry seasonality, and imply that trees may have established during a short-lived pluvial phase when the region was wetter. The Socorro fossil forest is important for two reasons. It contains the oldest examples of unequivocal conifers in growth position, and provides a glimpse of the enigmatic coniferopsid ecosystems that are inferred to have covered much of seasonal tropical Euramerica, but are rarely preserved due to taphonomic megabias.

A new Late Devonian genus with seed plant affinities.

BackgroundMany ovules of Late Devonian (Famennian) seed plants have been well studied. However, because few taxa occur with anatomically preserved stems and/or petioles, the vascular system of these earliest spermatophytes is little understood and available data come mostly from Euramerica. There remains great controversy over the anatomical differentiation of Late Devonian and Carboniferous seed plant groups of Buteoxylonales, Calamopityales and Lyginopteridales. Protostele evolution of these early spermatophytes needs more research.ResultsA new taxon Yiduxylon trilobum gen. et sp. nov. with seed plant affinities has been discovered in the Upper Devonian (Famennian) Tizikou Formation of Hubei Province, China. It is represented by stems, helically arranged and bifurcate fronds with two orders of pinnae and planate pinnules. Both secondary pinnae and pinnules are borne alternately. Stems contain a small protostele with three primary xylem ribs possessing a single peripheral protoxylem strand. Thick secondary xylem displays multiseriate bordered pitting on the tangential and radial walls of the tracheids, and has biseriate to multiseriate and high rays. A narrow cortex consists of inner cortex without sclerotic nests and sparganum-type outer cortex with peripheral bands of vertically aligned sclerenchyma cells. Two leaf traces successively arise tangentially from each primary xylem rib and they divide once to produce four circular-oval traces in the stem cortex. Four vascular bundles occur in two C-shaped groups at each petiole base with ground tissue and peripheral bands of sclerenchyma cells.ConclusionsYiduxylon justifies the assignment to a new genus mainly because of the protostele with protoxylem strands only near the periphery of primary xylem ribs, leaf trace origination and petiolar vascular supply structure. It shares many definitive characters with Calamopityales and Lyginopteridales, further underscoring the anatomical similarities among early seed plants. The primary vascular system, pycnoxylic-manoxylic secondary xylem with bordered pits on both tangential and radial walls of a tracheid and leaf trace divergence of Yiduxylon suggest transitional features between the early spermatophytes and ancestral aneurophyte progymnosperms.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0292-6) contains supplementary material, which is available to authorized users.

Coniferopsid tree trunks preserved in sabkha facies in the Permian (Sakmarian) Community Pit Formation in south-central New Mexico, U.S.A.: Systematics and palaeoecology

We describe the anatomy of silicified tree trunks found in the lower Permian (Sakmarian) Community Pit Formation (Hueco Group) near Las Cruces, south-central New Mexico, U.S.A. The fossils occur as allochthonous assemblages within facies interpreted as supratidal sabkha deposits in a dominantly shallow marine carbonate-siliciclastic succession, and probably represent remains of forests that fringed a seasonally dry coast. Although several hundred specimens were collected, only ten specimens, interpreted as derived from near the crowns of large trees, showed sufficiently good preservation of pith and primary vasculature for full description. The dominant taxon is Macdonaldodendron giganticus gen. et sp. nov., which shows a broad, non-septate pith containing sclerotic nests, an endarch, non-sympodial vasculature, helically arranged, triangular leaf bases embedded in the secondary xylem near the pith, and whorls of more than seven plagiotropic branches at some levels; it is interpreted as an evergreen walchian conifer. Somewhat rarer are two species of Giblingodendron gen. nov., which show a broad, non-septate pith, with sclereid cells, a mesarch, non-sympodial vasculature, and helically-arranged leaf traces that are occluded at the first ring boundary; this genus is interpreted as a deciduous coniferopsid, and probably, a voltzian conifer. One further incompletely preserved specimen is of Cordaixylon–Mesoxylon type and comprises a septate, homocellular pith, non-sympodial vasculature and, helically arranged leaf traces; it is probably cordaitalean. Macdonaldodendron lacks tree rings, whereas the two Giblingodendron species show marked tree rings, suggesting that the two genera employed varied phenological strategies and/or had different edaphic preferences in this seasonally dry region of western Pangaea. The fossil assemblage also demonstrates the diversity of early Permian tropical coniferopsid forests and challenges the view that late Palaeozoic conifers were exclusively small trees and shrubs.

A Ranunculalean Liana Stem from the Cretaceous of British Columbia, Canada:Atli moriniigen. et sp. nov.

Premise of research. The lianoid habit is found in 125 extant plant families and is most diverse and abundant in structurally complex forests, such as tropical forests. A stem with lianoid anatomy is described from Cretaceous sediments of Hornby Island, British Columbia.Methodology. The stem segment, 2.5 cm in diameter and 2.8 cm long, was studied using the cellulose acetate peel technique and SEM. Anatomy was documented and compared to fossil and modern taxa.Pivotal results. The stem lacks distinct growth increments, and the fibrous wood is dissected by large (>10 cells wide) rays. Wood is diffuse porous with mostly solitary vessels, rarely in tangential multiples (2–4). Vessel elements have a mean tangential diameter of 198 μm and mean length of 527 μm, bearing medium to large, crowded, elliptical to flat-elliptical alternate pits. Axial parenchyma is diffuse and vessels are surrounded by vasicentric tracheids with alternate bordered pitting. Rays are homocellular and >2 cm tall. Phloem rays are dilated, protruding into the xylem rays; thick-walled ray cells contain prismatic crystals. Periderm is composed of thin-walled cells interspersed with sclerotic nests. Wood anatomy of the fossil shows the most similarity to that of lianas in the Menispermaceae, Lardizabalaceae, and Ranunculaceae.Conclusions. The Hornby Island stem represents a new taxon, Atli morinii gen. et sp. nov. (Ranunculales). This liana specimen expands our knowledge of Cretaceous biodiversity and points to the presence of structurally complex forests on Hornby Island in the Campanian. Anatomy of Atli and other Cretaceous liana stems combines characteristics of several families in Ranunculales, documenting past anatomical diversity and possible stem lineage mosaicism. The most diverse lianoid lineages currently known from the Cretaceous and Paleogene are early-divergent eudicots, particularly Ranunculales and Vitales that account for more than 50% of described lianoid species during this key time period of angiosperm diversification.

Gymnosperm trees from the Permian of Antarctica: An anatomically preserved trunk of Kaokoxylon sp.

Anatomically preserved gymnosperm axes are relatively abundant in Permian localities of Antarctica, but their anatomy has rarely been studied in detail, which limits comparison with other Gondwanan morphotaxa. Here we describe a silicified trunk collected from the Upper Permian Buckley Formation at Coalsack Bluff, in the central Transantarctic Mountains. The trunk has a small heterogeneous pith approximately 4mm in diameter containing conspicuous sclerotic nests, endarch primary xylem maturation, paired leaf traces, and secondary xylem of the Araucarioxylon type. Comparison with contemporaneous gymnosperm axes from Antarctica indicates that the Coalsack Bluff trunk represents a new Permian morphotaxon for the region. The anatomical characters of the pith and secondary xylem suggest an affinity with the genus Kaokoxylon Kräusel, previously reported from Permian and Triassic localities of Southern Africa, South America, India, and Australia.

Pharmacognosy of Indian substitutes of male fern. I. Dryopteris ramosa (Hope) C. Chr. and D. chrysocoma (Christ) C. Chr.

Abstract A taxonomic description, and the macroscopy and microscopy of the rhizome and leaf bases of Dryopteris ramosa (Hope) C. Chr. and D. chrysocoma (Christ) C. Chr. are given. Both the species compare very favourably in oleoresinous content and “crude filicin” with the official male fern. Because of their abundance in nature they could be commercially exploited. Like the official male fern, both the species possess schizogenous cavities in the ground tissue with internal glands. D. ramosa is devoid of sclerotic nests while a few of these are present in the other species both in the rhizome as well as in the leaf bases.

Trawetsia princetonensis gen. et sp. nov. (Blechnaceae): A Permineralized Fern from the Middle Eocene Princeton Chert

Trawetsia princetonensis Smith, Stockey, Nishida & Rothwell gen. et sp. nov. is described from several permineralized rhizomes, stipes, and higher‐order frond members of a blechnoid fern that have been identified from the Middle Eocene Princeton Chert of British Columbia. Rhizomes bear stipes arising from all sides of the stem as well as diarch adventitious roots. The dictyostelic rhizomes are up to 16 mm across and have five to seven amphiphloic cauline bundles that are capped internally and externally by sclerenchyma. Ground tissue, where well preserved, is transitional from arenchymatous to parenchymatous, with abundant small sclerotic nests found throughout the pith and cortex. Multicellular scales are borne on the rhizome but are sparse and do not imbricate. At least three orders of frond material are preserved: stipes, primary pinnae, and laminar pinnules. Stipes have an adaxial groove, two adaxial hippocampiform bundles, and seven or fewer small, circular bundles arranged in an abaxial U‐shaped arc...

Conantiopteris schuchmanii, gen. et sp. nov., and the Role of Fossils in Resolving the Phylogeny of Cyatheaceae s.l.

gen. et sp. nov. The specimen, 23.2 cm long and 11.7 cm wide, shows helically arranged persistent frond bases embedded in adventitious roots, and is clothed by multicellular trichomes. A parenchymatous pith with mucilaginous cells and sclerotic nests is surrounded by an amphiphloic distyostele, parenchymatous inner cortex, and outer sclerenchymatous cortex. Sclerenchyma also surrounds the cauline vasculature and leaf traces. Medullary and cortical bundles are absent. Phloem contains both axially elongated and tangential sieve elements. Frond bases are oval in outline with three vascular bundles, including an undulating abaxial arc and an adaxial pair. Protoxylem of the stipe is endarch and is associated with cavity parenchyma. These characters are indicative of tree fern affinities. A cladistic analysis using trunk characters of both living and fossil tree ferns was conducted to help establish relationships of the new species and other fossil ferns, and to test hypotheses of general tree fern relationships. Additional analyses of living taxa only were also performed. Results from the analysis using both living and fossil taxa compare favorably with those that included only living species when either morphological characters or molecular sequences of the chloroplast gene rbcL are utilized. Although there are variations in the topologies of the various trees, results indicate that the new genus is nested among a paraphyletic assemblage of dicksoniaceous, lophosoriaceous, and metaxyaceous species that subtend a monophyletic Cyatheaceae s.s.

Studies on a lower carboniferous flora from kingswood near pettycur, Scotland. III. Lyginorachis

Two new species of Lyginorachis, a genus of petioles and rachises of pteridosperm affinities, are described from the Upper Visean locality of Kingswood. L. camptovenis sp. nov. is characterized by a V-shaped vascular strand and the occurrence of elongated secretory cells in the inner cortex. L. kingswoodense sp. nov. resembles L. kidstonii from the Upper Tournaisian deposits of Berwickshire (Scotland) in possessing a C-shaped vascular strand. Sclerotic nests are present in the inner cortex. In most-specimens of L. kingswoodense lysigeneous secretory cavities resulting from the breakdown of short secretory cells occur in both the inner and outer cortex. A discussion of the genus Lyginorachis is provided.

Seed fern (Dictyastrum chestriensis n. gen. and sp.) with a Dictyoxylon-type cortex from the Upper Mississippian of the Illinois Basin

Dictyastrum chestriensis n. gen. and sp. is a seed fern that occurs in the Chester Series (Upper Mississippian) of the Illinois Basin, and is based on compressions, impressions, and pyritemarcasite petrifactions of the stem and frond. The stem has a mixed prostele with indistinct protoxylem, and the larger specimens have a thin zone of secondary xylem that contains many small rays. The inner cortex contains numerous transversely-oriented sclerotic nests, whereas the outer cortex contains prominent anastomosing fiber bundles that produce the Dictyoxylon-type pattern that is frequently observable on compressions and impressions. The petiole is massive, has an expanded base, and forks distally into unequal subdivisions. The distal frond has small pinnules with rounded lobes and corresponds to the form species Sphenopteris stricta (=S. bermudensiformis), which is used for isolated compressions and impressions. Dictyastrum chestriensis belongs to the Lyginopteridales and is intermediate morphologically between Lyginopteris and Heterangium.

Observations on Eristophyton Zalessky, Lyginorachis waltonii Calder, and Cladoxylon edromense sp. nov. from the Lower Carboniferous Cementstone Group of Scotland

ABSTRACTFifteen specimens of Eristophyton stems from the Lower Carboniferous Cementstone Group of Berwickshire and East Lothian have been examined. Three possess medullary rays comparable to E. waltonii Lacey, the others have rays like E. beinertianum (Göpp.) Zalessky. In one specimen assigned to E. waltonii a leaf-trace subdivides outside the secondary xylem to form an arc of six separate bundles. Another stem of E. waltonii has attached closely spaced petiole bases one of which is clearly identifiable as Lyginorachis with six vascular bundles arranged in an arc. Stems of Eristophyton from five localities occur associated with petioles or rachises possessing a U-shaped vascular bundle with abaxial ridges like L. waltonii Calder. As these may occur mixed with rachises agreeing with L. brownii Calder the latter is regarded as synonymous. Detached petioles found associated with E. beinertianum may possess four or six basal bundles. The evidence suggests that the U-shaped petiolar bundle passes down into four then six basal bundles and such petioles are associated with both E. waltonii and E. beinertianum. Calder (1935, pl. 1, fig. 2) showed dichotomy in the petiole bundle.In addition different rachises are known possessing a more massive U-shaped bundle but lacking sclerotic nests and sparganum outer cortex. These are assigned to Cladoxylon edromense sp. nov. Cortical nests occur in both E. waltonii and L. waltonii and may be compared with the sclerotic plates in the compressions of Diplotmema dissectum Brongn. and D. patentissimum Ett.. The evidence supports the view that Eristophyton is a pteridosperm with bifurcate fronds known as L. waltonii Calder when petrified and comparable to Diplotmema when compressed.

Stenomyelon from the Upper Tournaisian of the Montagne Noire (France)

Stenomyelon bifasciculare nov. sp. is described from the Tournaisian of the Montagne Noire. Represented by six fragments of stems measuring 25 to 40 mm in diameter, these fossil axes bear swollen petiole bases separated by short internodes. Anatomically, they are characterized by a mixed stele with eccentrically mesarch protoxylem poles, secondary xylem with tracheids pitted on all walls, petiolar traces of Kalymma type, and few sclerotic nests in the cortex. The divergence of a pair of leaf traces from each rib of the stele has given the taxon its specific epithet. This feature is new for the genus. Stenomyelon bifasciculare is more distinctive than the Scottish and American taxa described to date. Except for Stenomyelon heterangioides, in which this character is doubtful, no sympodia from which leaf traces diverge are recognized in any Stenomyelon, including Stenomyelon bifasciculare; protoxylem maturation has no cauline expression. This character is suggested as the most important one to define the genus.

Oxroadopteris parvusgen. et sp. nov.: a protostelic Lower Carboniferous pteridosperm from Oxroad Bay, East Lothian, Scotland

ABSTRACTOxroadopteris parvusgen. et sp. nov. is described from a single incomplete curved stem, 12 cm long and 8 mm diameter, having a cylindrical exarch protostele and sparganum outer cortex. Attached are 8 incomplete bifurcate petioles in probably 2/5 phyllotaxy. Each petiole has a swollen base with sclerotic nests. Petiole lengths increase upwards. Each petiolar trace is small, U-shaped in cross-section, bipolar, and divides to form similar smaller bundles in two secondary rachises.

The Morphology and Relationships of Rhodea, Telangium, Telangiopsis, and Heterangium

This study deals with four form or organ genera from the Upper Mississippian (Chester Series) of the Illinois Basin, and provides evidence that they were produced by a single natural genus with gymnospermous affinity. The plant remains—compressions, impressions, petrifactions, and specimens that combine compression or impression with petrifaction—allow examination of both external morphology and internal anatomy. The specimens include foliage corresponding to Rhodea, stems and petioles corresponding to Heterangium, and synangiate fructifications corresponding to either Telangium or Telangiopsis. The stems and foliage are considered parts of the same plant because of the identity of the anatomical and cuticular features of petioles attached to stem and those petioles with attached foliage. The fertile material is regarded as part of the same plant because: (1) The anatomy of axes of the fertile specimens is like that of the sterile specimens. (2) A single specimen may contain both sterile Rhodea-type axes and fertile regions. (3) Axes bearing synangia have the same size and patterns of divisions as the sterile foliage. Features that indicate lyginopterid affinities include: (1) Equal forking of the petiole. (2) Presence of fiber bands in the outer cortex and sclerotic nests in the inner part of the cortex. (3) Crowded circular bordered pits on the lateral walls of the metaxylem tracheids. (4) The presence of a small amount of secondary xylem. A variety of structural details of the stem and petiole suggest the genus Heterangium. The phyletic position of the plant that produced Rhodea, Telangium, Telangiopsis, and Heterangium is reviewed in light of such discoveries as the presence of a planated frond that lacks a lamina and the presence of both monolete and trilete microspores in a single synangium.

THE MORPHOLOGY AND RELATIONSHIPS OF RHODEA, TELANGIUM, TELANGIOPSIS, AND HETERANGIUM

This study deals with four form or organ genera from the Upper Mississippian (Chester Series) of the Illinois Basin, and provides evidence that they were produced by a single natural genus with gymnospermous affinity. The plant remains—compressions, impressions, petrifactions, and specimens that combine compression or impression with petrifaction—allow examination of both external morphology and internal anatomy. The specimens include foliage corresponding to Rhodea, stems and petioles corresponding to Heterangium, and synangiate fructifications corresponding to either Telangium or Telangiopsis. The stems and foliage are considered parts of the same plant because of the identity of the anatomical and cuticular features of petioles attached to stem and those petioles with attached foliage. The fertile material is regarded as part of the same plant because: (1) The anatomy of axes of the fertile specimens is like that of the sterile specimens. (2) A single specimen may contain both sterile Rhodea‐type axes and fertile regions. (3) Axes bearing synangia have the same size and patterns of divisions as the sterile foliage. Features that indicate lyginopterid affinities include: (1) Equal forking of the petiole. (2) Presence of fiber bands in the outer cortex and sclerotic nests in the inner part of the cortex. (3) Crowded circular bordered pits on the lateral walls of the metaxylem tracheids. (4) The presence of a small amount of secondary xylem. A variety of structural details of the stem and petiole suggest the genus Heterangium. The phyletic position of the plant that produced Rhodea, Telangium, Telangiopsis, and Heterangium is reviewed in light of such discoveries as the presence of a planated frond that lacks a lamina and the presence of both monolete and trilete microspores in a single synangium.

10.—Triradioxylon—a New Genus of Lower Carboniferous Petrified Stems and Petioles together with a Review of the Classification of Early Pterophytina

SynopsisTriradioxylongen. nov. is erected for petrified stems and petioles in which the primary xylem has a triradiate form and possesses protoxylem at the ends of the arms and in the central region. Secondary xylem is dense and composed of small tracheids having multiseriate bordered pits on all walls. Rays are narrow and high. The cortex has sclerotic nests and radial bands of fibres (sparganum structure).In the type speciesT. primaevumsp. nov. the petioles are borne 5–6 cm apart in a phyllotactic spiral of ⅓ on a stem about 1 cm (or more) diameter. The petiole is swollen at its base (about 8 mm diameter) and very gradually tapers to about 2 mm in the rachis which has not been seen to dichotomise. The length of petiole up to the first pinna may exceed 10 cm. Pinnae arose alternately and themselves branched. The T-shaped petiolar bundle has two protoxylem groups at the end of each arm and the central protoxylem divided into three in the rachis.Two detached rachises which cannot be assigned with certainty toTriradioxylon primaevumare placed in the genusLyginorachisand namedL. whitadderensissp. nov. In these the T-shaped vascular bundle is slightly larger than that in the rachises ofT. primaevumand the ends of the transverse arms are wider and may possess three protoxylem groups.The rachises in bothT.primaevumandL. whitadderensisbear alternate triarch pinna-traces but inL. whitadderensisa pair of sub-opposite monarch pinna-traces is also present.Triradioxylonis classified along withButeoxylonin the family Buteoxylonaceae placed tentatively asincertae sedisin the Pteridosperms although showing some affinity withAneurophytonin the Progymnospermopsida.

Pharmacognosy of Indian Substitutes of Male Fern II: Dryopteris barbigera and Dryopteris cochleata

A macroscopic and microscopic description of the rhizome and leaf bases of Dryopteris barbigera (Moore) O. Ktze. and D. cochleata (Don) C. Chr. is presented. Both the species compare very favorably in oleoresinous content and ‘crude filicin’ with the official male fern. The two species, described in this paper are differentiated from each other on the basis of the shape and size of the rhizome, structure of the ramenta present on the rhizomes, the presence and absence of dark sclerotic nests in the ground tissue, the number of cauline vascular bundles, and the shape and size of the stalk of internal secretory unicellular glandular hairs.

IV—On rhexoxylon, bancroft—a triassic genus of plants exhibiting a liane-type of vascular organisation

In 1913 Dr. Bancroft instituted the generic nameRhexoxylonfor a portion of a petrified stem sent by Dr. Rogers, Director of the Geological Survey of South Africa, to Prof. Seward for investigation. The specimen was handed over to Dr. Bancroft, who, in a communication to the Linnean Society of London, gave a full account of its anatomy.Rhexoylon, as represented by the type-specimen, may be briefly described as follows:— The fragment of stem exhibits “parts of two more or less concentric series of vascular structures surrounding a large pith and embedded in a parenchymatous ground-mass,” which contains sclerotic nests and small vascular strands. The pith, in addition to sclerotic nests and small vascular strands, contains other structures, which are most probably of an anomalous nature. There is an inner ring or series of vascular structures, which were called, for convenience in description, “steles”; each consists of two portions of secondary wood, one centrifugal and the other centripetal, separated by a narrow zone of obliterated cells. The “steles” branch and rarely anastomose. Traces were described separating from the sides of the centripetal portions of the “steles” and taking a centrifugal course. Outside and opposite each member of this inner series is a mass of centrifugally-developed secondary wood, on the inner margin of which are numerous small protoxylem groups. The tracheids have bordered pits, arranged typically in two alternating series; the pits are flattened and in contact. The medullary rays are uniseriate. Tissue external to the xylem was described as phloem.

Notes on Calamopitys, Unger.

In the first part of the paper additional evidence is brought forward as to the course of the leaf-trace in Calamopitys americana. The trace, after separating from the reparatory strand, divides into two in traversing the zone of secondary wood. It thus differs from the trace of C. Saturni, in which division is only completed beyond the zone of thickening. The second part of the paper is devoted to a re-examination of the five species. In C. annularis the zone of primary xylem is almost if not quite continuous. The primary xylem-strands are, as a rule, eccentrically mesarch, the protoxylem lying nearer the outer side of the strand. Tubular elements, which are probably medullary tracheides, are present in the pith, indicating a protostelic structure. Each leaf-trace strand, on its exit from the wood, is surrounded by its own zone of secondary xylem. In all these points C. annularis agrees with C. americana. In the Halle specimen, a small branch referred by Solms-Laubach to C. annularis, the medullary rays are narrow, resembling those of C. fascicularis and C. Beinertiana. In C. Saturni the primary xylem-strands are found to be completely isolated; there is no continuous xylem-ring. The xylem-strands are, as a rule, centrally mesarch, with the centrifugal and centripetal portions equally developed. There is little or no indication of medullary tracheides. The three species, C. americana, C. annularis, and C. Saturni, all had Kalymma petioles of very similar structure. In C. fascicularis the leaf-trace strands at their exit from the small pith are of large size, centrally mesarch and perfectly similar to those of C. Saturni. Lower down in their course they diminish in size and the centripetal portion of the xylem becomes much reduced. The protoxylem of the leaf-trace divides into two in passing through the zone of secondary wood. The wood has narrow medullary rays and is generally of a Cordaitean type. Its inner layers consist of short, wide tracheides, suggesting a water-storing function. In C. Beinertiana the pith is large and contains sclerotic nests. The xylem-strands are similar to those of the preceding species, except that in the lower part of their course they become actually endarch. Division of the protoxylem has not been observed. The wood has a Cordaitean character. A synopsis of the five species is given on p. 221. The affinities of the species are then considered, with reference to Dr. Zalessky's proposed separation of C. fascicularis and C. Beinertiana under the generic name Eristophyton; the conclusion is reached that, while generic separation may ultimately be justified, all the five species form a natural series, in which C. Saturni occupies, in certain respects, an intermediate position, between C. annularis and C. americana on the one hand, and C. fascicularis and C. Beinertiana on the other. Lastly, the affinities of the genus are discussed. While the whole Calamopitys series should remain in Cycadofilices, the nearest affinity being with the Lyginopterideæ, through Heterangium, the species C. fascicularis and C. Beinertiana show some advance towards the structure of Cordaitales and especially of the family Cordaiteæ.