The developmental anatomy of Metaxya rostrata (Filicales: Metaxyaceae)

The systematically problematic fern Metaxya rostrata, commonly regarded as an ally of the cyatheoid and dicksonioid tree ferns, is investigated, and features of its organography, shoot vascular anatomy and development, soral initiation and early development, and gametophyte structure are described. The rhizome is creeping, dorsiventral, with an unusual four-seriate phyllotaxis. Typical protoxylem is lacking from the intemodes of the solenostele, but are present in the leaf trace and end blindly proximally. Tangential cells are found in the phloem of the stem. The early maturing “protoxylem” of the stem is scattered, and, apart from some identifiable protoxylem strands, is not clearly associated with the young leaves. Sori are initiated as groups of large cells on the abaxial side of developing leaflets, distant from the marginal meristem initials, and in close association with a lateral vein. Two sori may arise by the subdivision of a single large patch of cells. Soral maturation is of the simple type. Gametophytes are cordate to ribbonlike, with moderately primitive gametangia. Morphologically and systematically, Metaxya appears isolated. It shares few significant derived conditions with the tree ferns, and a separate family Metaxyaceae seems well justified.     

Comparative development of heavily asymmetric-cordate gametophytes of <Emphasis Type="Italic">Anemia phyllitidis</Emphasis> (Anemiaceae) focusing on meristem behavior

Development of heavily asymmetric cordate gametophytes of Anemia phyllitidis (Anemiaceae), one of the schizaeoid ferns, was examined using a sequential observation technique; epi-illuminated light micrographs of the same growing gametophytes were taken approximately every 24 h. The apical cell-like wedge-shaped cell was produced once from the terminal cell of a germ filament, but it stopped dividing soon after production of one or two derivative cells. Without a functional apical cell, the gametophyte developed by intercalary growth until the early stage of wing formation, and then the multicellular (pluricellular) meristem arose from the lower lateral side of the gametophyte. This was in sharp contrast to the observation that the multicellular meristem forms in place of the apical cell in typical cordate gametophytes. Loss of the functional apical cell probably caused a site-shift in the multicellular meristem of the Anemia phyllitidis gametophyte during evolution from apical to lateral. The results suggest that apical cell-based and multicellular meristems are primarily independent of each other. The multicellular meristem produced cells equally in the distal and proximal directions to form wings in both directions but proximally produced cells divided much less frequently. As a result, a heavily asymmetric gametophyte was formed.     

COMPARATIVE MORPHOGENESIS OF THE DIMORPHIC LEAVES OF CYAMOPSIS TETRAGONOLOBA

Cyamopsis tetragonoloba, guar, produces two leaf forms: a simple leaf and a trifoliate leaf. The steps in the development of each of these forms have been investigated in an attempt to determine the precise point at which the leaf primordium becomes destined to produce one or the other characteristic leaf shapes. Up to 140 μ in length the leaf primordia are morphologically indistinguishable. If a simple leaf is to be formed the marginal meristem remains continuous and initiates only lamina. If a trifoliate leaf is to be formed the continuity of the marginal meristem is interrupted by a group of “pocketal” cells dividing it into an upper lamina meristem and a basal leaflet buttress.     

DIFFERING ONTOGENETIC ORIGINS OF PCR (“KRANZ”) SHEATHS IN LEAF BLADES OF C4 GRASSES (POACEAE)

The origin and early development of procambium and associated ground meristem of major and minor veins have been examined in the leaf blades of seven C₄ grass species, representing different taxonomic groups and the three recognized biochemical C₄ types (NAD-ME, PCK, and NADP-ME). Comparisons were made with the C₃ species, Festuca arundinacea. In “double sheath” (XyMS+) species (Panicum effusum, Eleusine coracana, and Sporoboìus elongatus), the procambium of major veins gives rise to xylem, phloem, and a mestome sheath; associated ground meristem differentiates into PCA (“C₄ mesophyll”) tissue and the PCR (“Kranz”) sheath. Development in the C₃ species parallels this pattern, except that associated ground meristem differentiates into mesophyll and a parenchymatous bundle sheath. In contrast, major vein procambium of “single sheath” (XyMS–) species (Panicum bulbosum, Digitaria brownii, and Cymbopogon procerus) differentiates into xylem, phloem and a PCR sheath; associated ground meristem gives rise to PCA tissue. These observations of major vein development support W. V. Brown's hypothesis that the PCR sheaths of “double sheath” (XyMS+) C₄ grasses are homologous with the parenchymatous bundle sheaths of C₃ grasses, while in “single sheath” (XyMS–) C₄ species they are homologous with the mestome sheath. Although there are some similarities in the development of the major and minor vascular bundle procambium in the C₄ species examined, the ontogeny of the smaller minor veins is characterized by a precocious delineation of the PCR sheath layer that may even precede the appearance of the distinctive cytological features of ground meristem and procambium. This contracted development in minor veins appears to be related to their close spacing in mature leaves and to their comparatively late appearance during leaf ontogeny.     

FLORAL DEVELOPMENT IN SAURURUS CERNUUS (SAURURACEAE): 1. FLORAL INITIATION AND STAMEN DEVELOPMENT

The inflorescence of Saururus cernuus L. produces lateral “common” primordia in acropetal succession on the flanks of the inflorescence meristem; curiously, the “subtending” bract is initiated upon the lateral primordium rather than subtending it. On the basis of mature floral structure, flowers of S. cernuus have previously been described as having spiral initiation of parts. The current ontogenetic investigation contradicts this interpretation. Stamens arise in three successive pairs; the carpels also are initiated in pairs. Floral symmetry is shown to be bilateral from the onset of organ initiation, a rare feature among primitive angiosperms. On the basis of symmetry and paired initiation of organs, the possibility of close relationships between Saururaceae and Magnolialian or Ranalian lines appears remote.     

Parallel evolution of an alpine type ecomorph in a scorpionfly: Independent adaptation to high‐altitude environments in multiple mountain locations

Elucidation of the diversification process of organisms is one of the important tasks of biology. From the viewpoint of species diversity, insects are the most successful group among the diverse organisms on earth and evolutionary adaptation is one of the important factors driving this pattern. Evolutionary adaptation is one of the important factors in the diversification of insects. One of the representative examples of environmental adaptation in insects is the shortening and loss of wings in subalpine and alpine zones. In this study, we focused on the Japanese scorpionfly, Panorpodes paradoxus. In this species, individuals that inhabit mountainous regions and subalpine zones have long wings (the “general type”), and individuals that inhabit higher altitudinal ranges have short wings (the “alpine type”). We collected samples of all Japanese Panorpodes species and one Korean Panorpodes species, and conducted molecular phylogenetic analyses of the mtDNA COI (610 bp), COII (688 bp), and 16S rRNA (888 bp) and nuDNA EF1‐α (658 bp) and 28S rRNA (524 bp) regions in order to reveal the evolutionary history of the alpine type of P. paradoxus. As a result of molecular phylogenetic analyses, it was revealed that the alpine type of P. paradoxus was polyphyletic, and had evolved to become the alpine type at least twice independently at separate mountain locations. In addition, the result of divergence time estimation suggested that the alpine type is an “ecomorph”, having recently adapted to low temperature habitats following mountain uplift within the Japanese Archipelago and subsequent glacial‐interglacial cycles.     

Developmental morphology of strap-shaped gametophytes of Colysis decurrens: a new look at meristem development and function in fern gametophytes

Background and Aims

The gametophytes of most homosporous ferns are cordate–thalloid in shape. Some are strap- or ribbon-shaped and have been assumed to have evolved from terrestrial cordate shapes as an adaptation to epiphytic habitats. The aim of the present study was to clarify the morphological evolution of the strap-shaped gametophyte of microsoroids (Polypodiaceae) by precise analysis of their development.

Methods

Spores of Colysis decurrens collected in Kagoshima, Japan, were cultured and observed microscopically. Epi-illuminated micrographs of growing gametophytes were captured every 24 h, allowing analysis of the cell lineage of meristems. Light microscopy of resin-sections and scanning electron microscopy were also used.

Key Results

Contrary to previous assumptions that strap-shaped Colysis gametophytes have no organized meristem, three different types of meristems are formed during development: (1) apical-cell based – responsible for early growth; (2) marginal – further growth, including gametophyte branching; and (3) multicellular – formation of cushions with archegonia. The cushion is two or three layers thick and intermittent. The apical-cell and multicellular meristems are similar to those of cordate gametophytes of other ferns, but the marginal meristem is unique to the strap-shaped gametophyte of this fern.

Conclusions

The strap-shaped gametophytes of C. decurrens may have evolved from ancestors with a cordate shape by insertion of the marginal meristem phase between the first apical-cell-based meristem and subsequent multicellular meristem phases. Repeated retrieval of the marginal meristem at the multicellular meristem phase would result in indefinite prolongation of gametophyte growth, an ecological adaptation to epiphytic habitats.     

FLOATING STOMATES (ADETOSTOMY) IN FERNS: DISTRIBUTION AND ONTOGENY

A unique guard cell apparatus occurs in certain species of Anemia (Schizaeaceae) and in certain species of the unrelated family Polypodiaceae. A guard cell pair is completely surrounded by one epidermal cell, with no attachment to lateral (anticlinal) walls of adjacent epidermal cells. This condition of “floating stomates” is called adetostomy. In rare cases the surrounding epidermal cell is in turn entirely enclosed by another single epidermal cell. The ontogeny of floating stomates has been variously interpreted. This study supports the early view of Rauter that a funnel-shaped guard mother cell is initiated in place entirely within a protodermal cell.     

PHYLOGENETIC TRANSITIONS IN THE CHLOROPLASTS OF THE ANTHOCEROTALES I. THE NUMBER AND ULTRASTRUCTURE OF THE MATURE PLASTIDS

Representatives of three genera of anthooerotes were examined: Phaeoceros, Notothylas, and Megaceros. Species of the first two genera were found to exemplify the typical anthocerote plastid condition. This condition is characterized by the presence in each cell of the gametophyte of only a single large chloroplast containing a “multiple” pyrenoid. The genus Megaceros, however, proved to be quite different. In two species of Megaceros the pyrenoid was observed to be composed of a highly subdivided thylakoid system of even greater complexity than the “multiple” pyrenoids of Phaeoceros. In another species only an indistinct “pyrenoid-like” area was noted while in a fourth species no evidence was found for any internal differentiation. Associated with these changes in plastid structure there are corresponding alterations in the number and the size of the chloroplasts. Together they indicate an evolutionary trend away from a primitive, algal-like condition to a more advanced land plant form.     

ONTOGENY OF THE OPEN DICHOTOMOUS VENATION IN THE PINNA OF THE FERN NEPHROLEPIS

Pray , Thomas r . (U. South. California, Los Angeles.) Ontogeny of the open dichotomous venation in the pinna of the fern Nephrolepis. Amer. Jour. Bot. 47(5) : 319—328. Illus. 1960.–The venation of the pinna of Nephrolepis consists of a midvein and 2 lateral series of dichotomizing veins all of which terminate freely near the margins. The development of the pinna is analyzed with particular attention to the nature of the marginal meristem and the organization of the embryonic pinna as it appears in paradermal section. The arrangement of cells in pinna wings during the period of marginal growth displays a pattern which foreshadows the pattern of the mature venation. In contrast with the development of the leaves of angiosperms, marginal growth continues into a relatively late phase of pinna ontogeny and apparently is active throughout the phases of ontogeny concerned with blocking-out the pathways of procambial differentiation. Thus the pattern of venation appears to be correlated with the manner of activity of the marginal meristem and subsequent orientation of its derivatives. The theoretical aspects of the result of this investigation are discussed in relation to other studies of foliar venation ontogeny.     

LEAF DEVELOPMENT IN SENECIO ROWLEYANUS (COMPOSITAE)

Prolonged apical growth of the leaf primordium and the presence of distinct marginal meristems do not occur in Senecio rowleyanus. Intercalary cell divisions accompanied by radial expansion of derivatives from an adaxial meristem account for the spherical shape of the leaf. The “window” in the lamina marks the position of the adaxial meristem and precludes interpretation of the leaf as being unifacial. Stomata are mesoperigenous and anomocytic in type. Schizogenous secretory canals occur in both the leaf and the stem, and their association with vascular bundles is discussed. The anatomy of the leaf is interpreted in terms of xeromorphy.     

BesitztAnemia Sori? Untersuchungen über die Entwicklung des Sporophylls vonAnemia phyllitidis (Schizaeaceae)

Observations of young fertile leaf primordia provide information about the development of the sporophyll ofAnemia phyllitidis Sw. The marginal meristem which surrounds the leaf primordium forms the pinna primordia, firstly the two “spore pinnae” by meristem fractionation. These are turned with their adaxial side towards the leaf apex and continue marginal meristem fractionations until products of the 5th order are formed.—In the sporophyll development two events are significant: (1) The fractionation products of the 2nd order reverse their direction of coiling. (2) From the marginal meristem of the fractionation products of the 5th order the sporangia arise in acropetal succession each originating from one initial cell.—Three observations—the fractionation products of the 2nd order being accessory outgrowths of the leaf margin, their reversed coiling direction, and the aggregation of the sporangia on the last segments—lead to the following concept of a sorus type: Each fractionation product of the 2nd order represents a marginal acropetal sorus with a branched receptaculum.     

QUANTITATIVE STUDIES OF PINNULE DEVELOPMENT IN THE FERNS ADIANTUM RADDIANUM AND CHEILANTHES VIRIDIS

Pinnule development was investigated in two fern species, Adiantum raddianum Presl cv. Decorum and Cheilanthes viridis (Forsk.) Swartz, by using clearings to facilitate the recording of mitotic divisions. Both species were found to possess a marginal meristem. This meristem consists of both a marginal row of large initials and a submarginal meristematic zone. The marginal meristem in these ferns is responsible for establishing the layers of the lamina, providing new cells which by enlargement will expand the pinnule, establishing general pinnule form, initiating the procambial stands, and forming the false indusia. The cells of the submarginal meristem were found to divide parallel to the pinnule margin more frequently if they were to become ground tissue, while dividing perpendicular to the margin more frequently if they were to become procambial. Details of vein dichotomies were also studied. Perimeter expansion was found to be associated with dichotomy of the veins, and venation pattern was found to be correlated with leaf form. The marginal meristem is active from the time of pinnule initiation until the pinnule reaches about 50% of its final length or width. Leaf development in leptosporangiate ferns resembles the traditional concept of development in angiosperms somewhat more than it does the more recent concepts. It is clear, though, that there is not a high degree of convergence in the marginal growth of fern and angiosperm leaves.     

Ontogeny and Marginal Growth in the Leaf of Eubrachion ambiguum

Marginal growth in the leaf of Eubrachion ambiguum, a viscaceoushemiparasite, has been investigated. This growth is accomplishedby the marginal meristem comprising the marginal initials aloneas has been described earlier by Hara (1957) in Daphne odora.To the best of the author's knowledge the present communicationis the second report of such a type of marginal growth in thedicotyledons. Phylogenetically, at least in Eubrachion ambiguum, it probablyrepresents a reduced rather than a primitive feature.     

SPORE MORPHOLOGY OF ANEMIA,MOHRIA, AND CERATOPTERIS (FILICALES)

Spores of the ferns Anemia and Mohria (Schizaeaceae) and Ceratopteris (Pteridaceae) are surveyed with light microscopy and scanning and transmission electron microscopy. In each genus the spores are trilete with radially symmetrical exine sculpture comprising three sets of parallel or near-parallel muri. Anemia has six spore types. One is reticulate (A. wrightii-type), and the other five types have either cicatricose or canaliculate sculpture that reflect a basic form, i.e., three mural sets that have mutual anastomoses in each radial region. The cicatricose A. mexicana- and the canaliculate A. dregeana-types represent the simplest expressions of this pattern. Specializations include cicatricose, auriculate (A. raddiana-type) and canaliculate, ornate (A. oblongifolia-, A. phyllitidis-types). Exine structure is homogeneous or differentially microporate; the enveloping two-layered perine has granulate structure and a granulate to spiculate and/or pitted surface. Mohria spores have a stratified, granulate to rugulose perine and cicatricose exine sculpturing consistent with the A. mexicana-type pattern, but the muri are hollow. The canaliculate spores of Ceratopteris differ from those of Anemia and Mohria in that the three mural sets are discrete and separated from each other by a stria in each radial region; exine structure is homogeneous and the thin perine is granulate. Within Anemia the A. raddiana-type is exclusive to subgen. Coptophyllum and the A. oblongifolia- and A. phyllitidis-types to subgen. Anemia. Three spore types are shared by two subgenera; i.e., A. wrightii- and A. mexicana-types in Coptophyllum and Anemirhiza, and the A. dregeana-type in Anemirhiza and Anemia. Spore polymorphism is indicated in several species of subgen. Anemia, and smooth immature spores are recorded from all three subgenera.     

THE DEVELOPMENT OF THE FEMALE GAMETOPHYTE OF EPIPACTIS (ORCHIDACEAE) AND ITS INFERENCE FOR REPRODUCTIVE ECOLOGY

The development of the female gametophytes of Epipactis atrorubens, E. helleborine, and E. palustris have been investigated using confocal scanning laser microscopy. These species have T-tetrads and eight-nucleate female gametophytes in common. The development of the female gametophyte is monosporic in accordance with the Polygonum type. Furthermore, the outer integument grows slowly and reaches to the middle of the inner integument, when the female gametophyte is mature. In the first two species, T-tetrads develop prior to anthesis, which may be correlated with autogamy. The development of the female gametophyte of E. palustris appears to be similar in plants from different localities.     

Novel mutant phenotypes of a dark-germinating mutant<Emphasis Type="Italic"> dkg1</Emphasis> in the fern<Emphasis Type="Italic"> Ceratopteris richardii</Emphasis>

The mutant dark-germinating 1 (dkg1) of the fern Ceratopteris richardii was originally characterized by two phenotypes, germination in the dark and inhibition of germination by light. In this work, we examined whether other phenotypes are present in the gametophytic generation of the dkg1 mutant. Although dkg1 prothalli grown in darkness were elongated as in the case of the wild type, some developmental processes were found to proceed even in complete darkness: (1) the apical and subapical zones developed largely by forming a lateral meristem; (2) asymmetric cell division for rhizoid differentiation occurred in the subapical elongation zone; (3) an archegonium was formed in the proximity of the meristem; and (4) chloroplast relocation could occur without de novo protein synthesis. Furthermore, these processes were shown to be under the control of phytochrome in the wild-type gametophytes on the basis of red/far-red reversibility. These results indicate that the DKG1 gene is pleiotropic and is involved in several phytochrome-mediated responses in the gametophyte development of C. richardii.     

The crescent of foramina in Australopithecus afarensis and other early hominids

The crescent of foramina of the cerebral surface of the sphenoid bone (superior orbital fissure, foramen rotundum, foramen ovale, foramen spinosum) differs morphologically in the African great apes and modern humans. New discoveries of Australopithecus afarensis at Hadar, Ethiopia, draw attention to the similarity of the crescent, particularly the “foramen” shape of the superior orbital fissure and its close proximity to the foramen rotundum, in this species, the African apes, and many other primates. Australopithecus africanus also shows this primitive pattern, whereas “robust” australopiths and humans share a configuration in which a true, laterally extended superior orbital fissure intervenes between the greater and lesser wings of the sphenoid and a broad bridge of bone separates the fissure from the foramen rotundum. This shared morphology may be added to the list of putative “robust” australopith-Homo synapomorphies. © 1996 Wiley-Liss, Inc.     

ANATOMY OF THE GYNOECIUM IN TWO SPECIES OF BAKERIDESIA (MALVACEAE)

Structure of the gynoecium is described in two species of Bakeridesia, subgenus Bakeridesia (Malvaceae, tribe Malveae). The dorsal wall of each carpel bears a winglike projection with a marginal pair of pubescent, bluntly dentate wings. The projection arises as a single, solid ridge of tissue after the ovules are initiated and after the ventral carpellary margins are fused with the receptacle. Two multiseriate layers of fiber-sclereids line each locule and continue into the winglike projection where they are separated by parenchyma. Gynoecial vascularization is described in detail. The richly vascularized carpels are supplied by five traces: a median dorsal trace, which bifurcates into two dorsal bundles; two lateral traces; and two ventral traces. Adjacent ventral traces, lateral traces, and septal bundles are fused—i.e., they are held in common by neighboring carpels. The presence of lateral carpellary traces may be a primitive character in the tribe Malveae.     

PHYLOGENETIC AFFINITIES OF “CHANTRANSIA” STAGES IN MEMBERS OF THE BATRACHOSPERMALES AND THOREALES (RHODOPHYTA)1

This study evaluated the phylogenetic relationship among samples of “Chantransia” stage of the Batrachospermales and Thoreales from several regions of the world based on sequences of two genes—the plastid‐encoded RUBISCO LSU gene (rbcL) and the nuclear SSU ribosomal DNA gene (SSU rDNA). All sequences of “Chantransia macrospora” were shown to belong to Batrachospermum macrosporum based on both molecular markers, confirming evidence from previous studies. In contrast, nine species are now associated with “Chantransia pygmaea,” including seven species of the Batrachospermales and two of the Thoreales. Therefore, the presence of “C. macrospora” in a stream can be considered reliable evidence that it belongs to B. macrosporum, whereas the occurrence of “C. pygmaea” does not allow the recognition of any particular species, since it is associated with at least nine species. Affinities of “Chantransia” stages to particular taxa were congruent for 70.5% of the samples comparing the rbcL and SSU analyses, which were associated with the same or closely related species for both markers. Sequence divergences have been reported in the “Chantransia” stage in comparison to the respective gametophyte, and this matter deserves further attention.