ACAULANGIUM GEN. N., A FERTILE MARATTIALEAN FROM THE UPPER PENNSYLVANIAN OF ILLINOIS

Material described by Graham as Cyathotrachus bulbaceus is believed to represent a new genus that is a common constituent of Upper Pennsylvanian coal balls. The sessile synangia of Acaulangium gen. n. are borne in a row on either side of the pinnule midrib and are composed of four to six short, tapering, laterally appressed sporangia. The sporangia have extended tips which curve over the inside of the synangium distally and delimit a small open area inside the synangium. The outer facing walls of the sporangia are two to three cells thick throughout while the inner facing walls are uniseriate. During dehiscence the sporangia separate laterally and spore release results from the rupture of a row of elongate cells along the inner sporangium midline. Among species of Scolecopteris the new genus resembles S. illinoensis and S. minor var. parvifolia but differs in its sessile synangial attachment. The additional parenchyma present between sporangial cavities in the synangia of Acaulangium, and the tendency toward bilateral symmetry suggests an early stage in the evolution of a bivalve synangium such as is present in Marattia.     

Vascular floral anatomy of the east asianHeloniopsis orientalis (Thunb.) C. Tanaka (Liliaceae-Helonieae)

Observations on the vascular floral anatomy, carpel morphology and floral biology ofHeloniopsis orientalis are presented. The lower flowering pedicel has six large bundles which lack an enclosing sclerenchymatous sheath. At mid-pedicel, branch bundles originate via radial divisions from each of these bundles. Subsequently, there is a vascular ring of 12 bundles below the receptacle. The six smaller bundles which are derived from alternate pedicel bundles eventually establish all of the ventral gynoecium supply. The six larger bundles supply the tepals, stamens and dorsal gynoecial vasculature. The simple dorsals do not branch or fuse in their vertical ascent. The ventral and placental supplies are far more complex. Fusion occurs between paired sets of the six smaller pedicel bundles along the septal radii and results in a submarginal laminal ventral network. An independent ventral plexus is formed in each septum and from each plexus two septal axials, of which the innermost has a reversed xylem-phloem disposition, and four placental bundles are derived. Two placental bundles are associated with each septal axial. Basally the septa are fused centrally, but are freed at mid-gymoecial height. The broadly tri-lobed, tri-carpellate gynoecium is depressed terminally where the erect, hollow style with its capitate stigma is attached. Dorsal grooves are present: the fruit is loculicidally dehiscent. There are no septal glands due to complete lateral fusion of the septal wings. Basally each of the six equal tepals has a saccate nectary. The similarity in vascular anatomy and carpel morphology of the AsianHeloniopsis and eastern North American endemic,Helonias bullata, justifies their position in the same tribe. Research and publication supported in part by the M. Graham Netting Research Fund through a grant from the Cordelia Scaife May Charitable Trust, the U. S.—Japan Cooperative Science Program Grant GF-41367, the Japan Society for the Promotion of Science, and Grant-in-Aid No. 934053 from the Ministry of Education, Japan.     

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.     

酢浆草叶片及花朵感夜运动的结构机制

为了解酢浆草(Oxalis corniculata)叶片和花朵的感夜性,采用半薄切片方法对其叶枕和花托进行形态解剖学观察。结果表明,黑暗处理酢浆草后叶片完全闭合,3枚叶片以叶轴为轴线向下紧贴闭合。黑暗处理8 h花瓣完全闭合并螺旋成束状,花萼紧贴螺旋的花瓣但不发生螺旋。叶片张开时屈肌侧皮层薄壁细胞收缩,伸肌侧皮层薄壁细胞膨大。叶片闭合时屈肌侧皮层细胞膨胀,伸肌侧表皮细胞和3～5层外皮层薄壁细胞收缩。花朵闭合时,花托基部的5个维管束收缩合并成2束明显分离的维管束群,且存在细胞壁加厚的现象;花托角隅处细胞膨胀。叶枕中的屈肌和伸肌细胞的收缩或膨胀控制酢浆草叶片的感夜运动,酢浆草花朵的感夜运动主要与花托基部的维管束群和花托角隅处细胞的膨大和收缩有关。     

Composite bundles,the host/parasite interface in the holoparasitic angiosperms Langsdorffia and Balanophora (Balanophoraceae)

Composite bundles are not simply a type of vascular bundles, but an integrated host/parasite interface. We investigated their structure in tubers of Langsdorffia and Balanophora. Composite bundles in both genera have similar components: 1) a central mass of host vascular tissues among which are located large parasite transfer cells; 2) a sheath of parasite parenchyma surrounding the central host vascular tissues; 3) specialized conducting tissues in the sheath; and 4) apical meristems composed of both host and parasite meristematic cells. Sheath parenchyma is recognizable from parasite tuber matrix by having thinner cell walls, and, especially in Langsdorffia, by the presence of collapsed matrix cells between the bundle sheath and tuber matrix. Sheath-conducting tissues consist of densely cytoplasmic transfer cells and small sieve tube members; in Langsdorffia, tracheary elements are also present. These sheath bundles connect with vascular bundles of the tuber matrix. Direct host/parasite contact only occurs by means of parasite transfer cells in the composite bundles. There is no xylem-xylem contact at the host/parasite interface. Abundance of parasite transfer cells suggests that they play an important role in nutrient absorption and translocation.     

ULTRASTRUCTURE OF CEPHALEUROS VIRESCENS (CHROOLEPIDACEAE; CHLOROPHYTA). I. SCANNING ELECTRON MICROSCOPY OF ZOOSPORANGIA

Scanning election microscopic examination of Cephaleuros virescens growing on leaves of Magnolia grandiflora has provided detailed observations which parallel, extend, and, in general, confirm previous light microscopic studies. The present study has revealed that in the ontogeny of terminal zoosporangia, apical zones form in the surface of an enlarged pyriform cell and that these zones, in some cases, are surrounded by a circumferential ridge, an external indication of an internal septum. A similar circumferential ridge is seen at the base of developing terminal zoosporangia. Contrary to some published accounts, the abscission of terminal sporangia does not commence with tearing of the pedicel-sporangium septal wall, but rather with an internal separation of the septum which is followed by a circumscissile tearing of the septal wall. The completion of abscission entails the emergence of a septal protuberance from the pedicel and/or the terminal sporangium in a process reminiscent of filament fragmentation in zygnematacean algae containing “replicate end walls.” Zoospore exit pores form in a lateral position on the terminal sporangia and are not coincident with the septal protuberances as has been reported in some recent accounts. Although both biflagellate and quadriflagellate zoospores have been seen in the light microscope, only the former have been observed with SEM. The SEM observations recorded in this study have provided a basis for comparison not only with light microscopic data, but also with transmission electron microscopic data which are now being recorded. Observations reported will be useful for interspecific and intergeneric comparisons.     

COMPARATIVE ANATOMY OF THE SEED COATS OF GNETUM AND THEIR PROBABLE EVOLUTION

The seed coats of Gnetum gnemon L., G. ula Brongn., G. montanum f. parvifolium (Warb.) Mgf. and G. neglectum Bl. consist of three layers. The outer layer or sarcotesta is mostly parenchyma but contains some sclereids and fibers and a series of simple vascular bundles. The middle sclerotesta forms masses of sclereids in varying shapes and numbers, sometimes extending as a basal plate, and is usually thicker near the micropylar tube. The second layer also contains a series of small vascular bundles that reach the apex. Depending on the species, the middle layer is sometimes nearly free from the outer layer, may be partially fused with it, or completely fused to it at maturity. The innermost layer of the seed coat constitutes the endotesta which is membranous and only rarely contains sclerenchyma. It possesses a dichotomous venation system with varying degrees of anastomosing, depending upon the species. The above species show qualitative and quantitative differences in their sclerenchyma and laticifers. Seed coat anatomy may be useful in the diagnosis of some species. The trends of evolution of seed coat structure within these four species of Gnetum are discussed, and a comparison of tissue layers and vasculature with certain fossil pteridosperms is made, especially in the Trigonocarpales     

ON THE STRUCTURE OF CALAMOSTACHYS BINNEYANA FROM THE LOWER PENNSYLVANIAN OF NORTH AMERICA

The discovery of specimens of Calamostachys binneyana in Lower Pennsylvanan petrifaction material in North America has provided additional information about the structure of this calamitean fructification. The cones consist of regularly spaced alternating whorls of bracts and sporangiophores. Bracts are fused in a disc except at the margin where the individual units become free. Sporangiophores are inserted at right angles to the cone axis and bear four axially directed sporangia. The vascular system of the North American specimens differs from that in other reports of the taxon in the presence of twelve vascular bundles in the cone axis. Each sporangiophore is supplied by a single vascular trace that departs from one axial bundle. There appears to be no constant relationship between the number of vascular bundles and the number of bracts. Spores are spherical, thin-walled, and of the Calamospora type. Relationships with other structurally preserved members in the genus are discussed in light of the diversity in structure demonstrated by the new specimens.     

IDANOTHEKION GEN. N., A SYNANGIATE POLLEN ORGAN WITH SACCATE POLLEN FROM THE MIDDLE PENNSYLVANIAN OF ILLINOIS

Idanothekion glandulosum gen. et sp. n. is a synangiate pollen organ represented by approximately 30 specimens contained in coal balls from the middle Pennsylvanian of Illinois. Each synangium is composed of seven to nine elongate sporangia that are fused laterally for approximately four-fifths of their length, and are radially arranged about, and fused to, a short central column; the central column is restricted to the proximal one-third of the synangium. Distal to the column the sporangia surround a hollow central area. Dehiscence occurred by means of a longitudinal slit along the mid-line of the inner face of each sporangium. The outer walls of the sporangia have a complex histology involving an external epidermis, a middle presumably glandular layer containing scattered enlarged cells, and an inner layer made up of thin-walled parenchyma. Vascular tissue is present in the central column and outer walls of the sporangia. Each sporangium has a prominent, attenuate, multicellular tip. Large numbers of saccate pollen grains similar to those found in numerous fossil and extant coniferophytes as well as some Mesozoic pter-idosperms were produced in each sporangium. Idanolhekion resembles some synangia assignable to Paleozoic members of the Marattiales; however, the new genus compares most closely with pollen organs believed to have been produced by members of the Pteridospermales. It seems most likely that Idanothekion represents the pollen organ of some member of the Lyginopteridaceae that produced pollen of a type which up to now has not been known from Paleozoic seed ferns.     

单芽狗脊营养器官的解剖学研究

采用离析法和石蜡切片法对单芽狗脊营养器官进行形态解剖研究。结果表明：单芽狗脊叶为异面叶,上、下表皮细胞均为不规则型,仅下表皮有气孔器分布;叶柄维管束有2~6个,自叶柄基部向上至叶轴仅有2个较大的维管束;根状茎薄壁细胞之间有多个维管束散生分布,且富含丰富的淀粉粒;皮层在根的横切结构中占比较大,木质部的发育方式为外始式;单芽狗脊珠芽的发育过程分为三个阶段,珠芽原基的形成期、珠芽原基的分化期、成熟期。     

Surface structure and anatomical aspects of Chinese brake fern (Pteris vittata; Pteridaceae)

The objective of this study was to describe a wide spectrum of surface structural and anatomical details of the Chinese brake fern (Pteris vittata) using scanning electron microscopy (SEM). SEM revealed that the epidermal cells of the pinnae were elongated with raised periclinal and sinuous anticlinal walls. The pinnae were hypostomatous with randomly scattered anomocytic stomatal complexes positioned at the same level as the epidermis. Stomates were large and elliptical (27.4 μm × 10.2 μm). Cross sections from the central regions of the rachis and the stipe revealed V- and U-shaped vascular bundles, respectively. In each vascular bundle, the xylem strands were sea-horse shaped (hippocampus). In contrast, the pinnae possessed a triangular vascular bundle with uniform mesophyll organization comprising of homogenous lobed parenchyma cells. The indumentum consisted of trichomes and scales, which formed various types of vestiture. Trichomes were borne only on the pinnae and scales on the rachis and stipe. The roots developed a dense network of long root hairs averaging 244 μm long, and the xylem consisted of tracheids with scalariform pitting. Sori were submarginal; continuous along both margins of the pinna and were covered with a false indusium. The sporangia were oblong with a short thick stalk and the annulus was positioned vertically resulting in transverse dehiscence of the sporangium. The paraphyses were uniseriate, unbranched, septate and found to be intermixed with the sporangia. The exine of the globose spores was adorned with thick reticulum in which the areoles contained round tubercles. This study describes surface features in detail, which is essential to studies examining the issue of whether morphological characteristics are related to arsenic hyperaccumulation inP. vittata.     

THE RELATIONSHIP BETWEEN THE PRIMARY THICKENING MERISTEM AND THE SECONDARY THICKENING MERISTEM IN YUCCA WHIPPLEI TORR. I. HISTOLOGY OF THE MATURE VEGETATIVE STEM

Anatomical observations were made on 1-, 2-, and 3-yr-old plants of Yucca whipplei Torr, ssp. percursa Haines grown from seed collected from a single parent in Refugio Canyon, Santa Barbara, California. The primary body of the vegetative stem consists of cortex and central cylinder with a central pith. Parenchyma cells in the ground tissue are arranged in anticlinal cell files continuous from beneath the leaf bases, through the cortex and central cylinder to the pith. Individual vascular bundles in the primary body have a collateral arrangement of xylem and phloem. The parenchyma cells of the ground tissue of the secondary body are also arranged in files continuous with those of the primary parenchyma. Secondary vascular bundles have an amphivasal arrangement and an undulating path with frequent anastomoses. Primary and secondary vascular bundles are longitudinally continuous. The primary thickening meristem (PTM) is longitudinally continuous with the secondary thickening meristem (STM). Axillary buds initiated during primary growth were observed in the leaf axils. The STM becomes more active prior to and during root initiation. Layers of secondary vascular bundles are associated with root formation.     

A fasciclin-domain containing gene, ZeFLA11, is expressed exclusively in xylem elements that have reticulate wall thickenings in the stem vascular system of Zinnia elegans cv Envy

The vascular cylinder of the mature stem of Zinnia elegans cv Envy contains two anatomically distinct sets of vascular bundles, stem bundles and leaf-trace bundles. We isolated a full-length cDNA of ZeFLA11, a fasciclin-domain-containing gene, from a zinnia cDNA library derived from in vitro cultures of mesophyll cells induced to form tracheary elements. Using RNA in situ hybridization, we show that ZeFLA11 is expressed in the differentiating xylem vessels with reticulate type wall thickenings and adjacent parenchyma cells of zinnia stem bundles, but not in the leaf-trace bundles that deposit spiral thickenings. Our results suggest a function for this cell-surface GPI-anchored glycoprotein in secondary wall deposition during differentiation of metaxylem tissue with reticulate vessels.     

ECCENTRIC SECONDARY GROWTH IN CORDYLINE AND OTHER AGAVACEAE (MONOCOTYLEDONAE) AND ITS CORRELATION WITH AUXIN DISTRIBUTION

Eccentric secondary growth is described and illustrated in detail for the first time in horizontal stems of Cordyline, Dracaena, Yucca and Beaucarnea (= Nolina) with up to 13 times more secondary tissues on the lower side than on the upper side. In Cordyline the secondary tissues on the lower side are rhizome-like in having less lignification of ground parenchyma and more diffuse and smaller secondary bundles than in the vertical stem. In Cordyline, Yucca, Beaucarnea, and D. reflexa the ground parenchyma cells are larger on the lower side. The vascular bundles are significantly larger on the lower sides of Beaucarnea and D. reflexa and are smaller on the lower side of D. fragrans. The occurrence of growth rings and eccentric growth is related to changes in cambial activity. There is close correspondence between enhanced cambial activity and high auxin levels on the lower side which have been reported elsewhere. However, there is no evidence of reaction wood tracheids on either the upper or lower sides.     

Ultrastructure of freeze-substitutedFrankia strain HFPCcI 3, the actinomycete isolated from root nodules ofCasuarina cunninghamiana

Summary Frankia strain HFPCcI 3 is an actinomycete isolated from root nodules ofCasuarina cunninghamiana. In culture it exhibits typicalFrankia morphology and may produce three distinct morphological forms: branching septate hyphae, terminal or intercalary sporangia, and specialized structures termed vesicles which are the purported site of nitrogenase activity. An examination of the ultrastructure of all three morphological forms using both conventional chemical fixation (CF) and quick-freezing followed by freeze-substitution (FS) reveals some interesting differences between the two fixation methods. Unique to FS material are: 1. smooth membrane profiles; 2. lack of mesosomes; 3. lack of discernible nucleoid regions with condensed chromatin; 4. clarity of cytoplasmic elements such as ribosomes and granular bodies; 5. large cytoplasmic tubules in hyphae and young sporangia; 6. outer wall layer not widely separated from the spherical portion of the vesicle, and 7. bundles of microfilaments in vesicles. The quality of preservation after FS appears to be far superior to that obtained with CF. Accordingly the structures observed after FS are thought to represent more faithfully the structure of the living cell.     

FLORAL ANATOMY OF IDIOSPERMUM AUSTRALIENSE (IDIOSPERMACEAE)

The floral anatomy of Idiospermum australiense (Diels) S. T. Blake is described from studies on relatively mature but unopened flower buds. The vascular system and general morphology of the flower is compared with that of Calycanthus and Chimonanthus (Calycanthaceae), especially with Calycanthus, the genus in which Diels originally placed Idiospermum. Inverted cortical bundles are present in both taxa but occur in different patterns. The tepals of Calycanthus are all 3-trace, whereas in Idiospermum only the upper tepals have three traces, the lower tepals having five to seven. All tepals of Calycanthus are spirally arranged; the lower tepals of Idiospermum are opposite or decussate in 1–3 pairs. The axial and recurrent bundle systems in Calycanthus are discrete except where the axial system turns downward, but in Idiospermum these systems, together with cortical bundles, are largely intermixed. The vascular supply to the carpel of Idiospermum, while possibly a modification of that of the carpels of Calycanthus, could also be interpreted as having an independent origin. Other differences and resemblances are described.     

VASCULAR PATTERNS IN STEMS OF THE CYCLANTHACEAE

A survey was made of the distribution of stem vascular bundles in representatives of ten genera of the tropical monocotyledonous family Cyclanthaceae. Films of series of serial transverse sections were used to reconstruct the stem vasculature. Each leaf trace, followed in a basipetal direction from its level of insertion at the stem periphery, describes an obliquely downward course, initially contacting from 1 to 4 (or more) existing axial bundles. The associated bundles form a compound vascular bundle in which the original bundles initially remain discrete, most commonly in a tetrapolar arrangement, with four separate strands. Followed further in the basipetal direction, the strands eventually fuse partly or completely, usually to form a collateral or amphivasal axial bundle which participates in a new structural cycle. Quantitative variation between different taxa includes a simple pattern in Ludovia, in which only bipolar bundles are developed. More elaborate forms have multipolar bundles with more than four separate strands. A systematically useful observation is that stem vasculature in Cyclanthus, representing the subfamily Cyclanthoideae, does not differ significantly from that in subfamily Carludovicoideae although there are some distinctive structural features.     

Chloroplast Development in Rye Coleoptiles

In the parenchyma cells of 1-d-old dark-grown rye coleoptiles (Secale cereale) proplastids occurred which sometimes contained starch grains. During coleoptile growth in darkness starch-filled amyloplasts are formed from the preexisting proplastids. No prolamellar bodies were observed in the stroma of the plastids of the etiolated coleoptile. After irradiation of 3-d-old etiolated coleoptiles with continuous white light three different types of plastids occurred. In the epidermal cells proplastids were observed. The parenchyma cells below the stomata of the outer epidermis (above the two vascular bundles) contained mature, spindle-shaped chloroplasts with a well-developed thylakoid system. In the parenchyma cells that surround the vascular bundles amyloplasts with some thylakoid membranes (chloroamyloplasts) occurred. The mesophyll cells of the primary leaves of dark-grown seedlings contained etioplasts with large prolamellar bodies. In the primary leaves of irradiated plants chloroplasts similar to those of the parenchyma cells of the coleoptile were observed. Our results show that the rye coleoptile, which grows underground as a heterotrophic organ, is capable of developing mature chloroplasts upon reaching the light above the soil surface. The significance of this expression of photosynthetic capacity for the carbon economy of the developing seedling is discussed.     

Plasmodesmatal distribution and frequency in vascular bundles and contiguous tissues of the leaf ofThemeda triandra

Small and intermediate vascular bundles and contiguous tissues of the leaf blade ofThemeda triandra var.imberbis (Retz.) A. Camus were examined with transmission and scanning electron microscopes to determine the distribution and frequency of plasmodesmata between various cell types. Plasmodesmata are most abundant at the mesophyll/bundle-sheath cell and bundle-sheath/vascular parenchyma cell interfaces, and their numbers decrease with increasing proximity to both thick- and thin-walled sieve tubes. Among cells of the vascular bundles, the greatest frequency of plasmodesmata occurs between vascular parenchyma cells, followed by that of plasmodesmata between vascular parenchyma cells and companion cells, and then by the pore-plasmodesmata connections between companion cells and thin-walled sieve tubes (sieve tube-companion cell complexes). The sieve tube-companion cell complexes of theT. triandra leaf are not isolated symplastically from the rest of the leaf and, in this respect, differ from their counterparts in theZea mays leaf. However, the thick-walled sieve tubes, like their counterparts inZea mays, lack companion cells and are symplastically connected with vascular parenchyma cells that about the xylem.Abbreviations SEM scanning electron microscope - TEM transmission electron microscope     

Pericarp histogenesis and histochemistry during fruit development in Butia capitata (Arecaceae)

Palm fruits show great structural complexity, and in-depth studies of their development are still scarce. This work aimed to define the developmental stages of the fruit of the neotropical palm Butia capitata and to characterize the ontogenesis of its pericarp. Biometric, anatomical, and histochemical evaluations were performed on pistillate flowers and developing fruits. The whole fruit develops in three phases: (I) histogenesis (up to 42 days after anthesis – DAA), when the topographic regions of the pericarp are defined; (II) pyrene maturation (42 to 70 DAA), when the sclerified zone of the pericarp is established; and (III) mesocarp maturation (70 to 84 DAA), when reserve deposition is completed. During pericarp ontogenesis (i) the outer epidermis and the outer mesophyll of the ovary give origin to the exocarp (secretory epidermis, collenchyma, parenchyma, sclerenchyma, and vascular bundles); (ii) the median ovarian mesophyll develops into the mesocarp, with two distinct topographical regions; (iii) the inner ovarian epidermis originates the endocarp; and in the micropylar region, it differentiates into the germination pore plate, a structure that protects the embryo and controls germination. (iv) Most of the inner region of the mesocarp fuses with the endocarp and, both lignified, give rise to the stony pyrene; (v) in the other regions of the mesocarp, carbohydrates and lipids are accumulated in a parenchyma permeated with fiber and vascular bundles. The development of the B. capitata pericarp presents high complexity and a pattern not yet reported for Arecaceae, which supports the adoption of the Butia-type pyrenarium fruit class.