古木蕨——云南早泥盆世一植物新属

本文报道了滇东南文山地区下泥盆统坡松冲组(西根阶)地层中一陆生植物新属、种——曲轴古木蕨(Gumuia zyzzata gen.et sp.nov.)。植物矮小,匍匐或直立生长,二叉分枝。能育轴上孢子囊侧出,居于顶端或侧部位置,后者呈亚对生、交互对生或互生在曲折能育轴的折点上。孢子囊圆至横椭圆形,无柄或极短柄,成熟时通常切线垂直茎轴着生,并沿远端开裂。在系统分类上,依据新植物孢子囊侧出的性状,它暂被归人工蕨类,这有待于解剖结构的进一步证实。文中还对合轴分枝这一重要性状的发生做了探讨。     

THE VASCULAR SYSTEM OF DOLEROTHECA AND ITS PHYLOGENETIC SIGNIFICANCE

The course of the vascular system in the proximal end of Dolerotheca formosa is described. Vascular bundles flare outward and downward immediately upon entering from the peduncle. These bundles are located in radiating septa just beneath the cover and give off small lateral bundles pinnately. Laterals from adjacent septal bundles meet, fuse, and extend downward in the parenchyma plate separating paired sporangia. The septal bundles, therefore, alternate in position with the parenchyma plate bundles and are interpreted as remnants of an ancestral bifurcating pinna system, which bore pendent sporangia along each side of supporting rachises. This interpretation differs from both the Codonotheca aggregation and plicated Whittleseya hypotheses recently advanced to explain the evolutionary pathway by which this complex pteridosperm pollen organ evolved.     

FOSSIL OPHIOGLOSSALES IN THE PALEOCENE OF WESTERN NORTH AMERICA

Vegetative and fertile frond segments of Botrychium have been recovered from Paleocene deposits of central Alberta, Canada. Specimens are preserved as coalified compressions that yield information about frond structure, sporangia, and spore ultrastructure. These fossils, described as Botrychium wightonii sp. nov., establish a megafossil record for the Ophioglossales, and demonstrate that modern-appearing species of the order were present in western North America by the earliest Tertiary. The largest vegetative fragments are up to 4.6 cm long and tripinnately compound, with opposite to subopposite branching. Ultimate segments are pinnatifid with dentate pinnules and open dichotomous venation. Fertile specimens are also tripinnately compound with a long rachis and subopposite to alternate pinnae. Sporangia are either submarginal and superficial, or marginal, and are all directed toward one surface of the pinnule. They are ovoid to subspheroidal and 0.8-2.0 mm in diameter. Some sporangia are apparently stalked, while others appear to be sessile. This variation results both from the ultimate frond segments being compressed in several different planes, and the fossils being exposed at different levels. Spores macerated from the sporangia are radial and trilete, and range 30–67 μm in diameter. Most are psilate, but some have a densely striate surface.     

Phytophthora irrigata, a new species isolated from irrigation reservoirs and rivers in Eastern United States of America

A new species of Phytophthora, previously referred to as the 'Dre I' taxon, is named Phytophthora irrigata. Isolates of P. irrigata morphologically and physiologically resemble Phytophthora drechsleri. They are heterothallic, produce nonpapillate sporangia, and grow well at 35 degrees C. The above two species differ significantly in uniformity of mycelium, presence of chlamydospores, DNA fingerprint, and sequences of multiple nuclear and mtDNA regions. Phytophthora irrigata produces smaller sporangia and a distinct DNA fingerprint. Sequence alignments in the ribosomal DNA internal transcribed spacer regions place Phytophthora fallax and Phytophthora captisoa as its closest relatives. The optimal temperature for culture growth is above 30 degrees C and the maximum temperature is 40 degrees C. This new species is abundant in irrigation reservoirs and natural waterways in Virginia and was also isolated in Pennsylvania.     

On Occurring of Sporangia of Protolepidodendron Krejci and Its Significance

This paper deals with the characteristics and occurring state of the sporangia of Protolepidodendron and its significance. The authors discovered that the sporangia with a short sporangiophore spread out from the axis of the fertile branch. There is a distance from the base of sporophyllary leaves to the setting point of the sporangiophore. Some sporangia divideinto suspended and symmetrical sporangia at the tip of the sporangiophore. But the most of sporangia do not divide. According to the characteristics of the sporangia of Protolepidodendron Krejci, which can be distinguished from genera Barrandeina (Krejci) Stur and Longos-tachys Zhu, Hu et Feng. Protolepidodendron lixianense sp. nov. is also described in this paper.     

SPORANGIAL FRAGMENTS REFERRED TO DICTYOPHYLLUM IN TRIASSIC CHERT FROJVI SARAWAR

Sporangial fragments of several Mesozoic fern taxa are organically preserved in a Triassic (Norian) chert from Sarawak. The more nearly entire annuli in the deposit are divided into two size classes. Structural features of the smaller annuli (capsule diam 0.26-0.3R mm) suggest affinities with the Gleicheniaceae, Matoniaceae, and Dipteridaceae. The three-dimensional preservation of the larger annuli (capsule diam 0.50-0.63 mm) reveals features of annular structure and stomial detail which are usually obscured in compressed specimens. Sporangia featuring these larger annuli were probably more-or-less pyriform and sessile, and they exhibited an oblique, uninterrupted annulus with greatly reduced induration in the stomial and hypostomial regions. The large size of these sporangia and their probable large spore number indicate that they are not conspecific with the Triassic Clathropteris meniscoides Brongn., also reported from Sarawak. On the basis of general morphology and their unusually large size, these sporangia are tentatively referred to Dictyophyllum exile (Brauns) Nathorst.     

中华水韭孢子囊发育研究

采用半薄切片法,连续观察了极度濒危级(CR)植物中华水韭大小孢子囊的发育过程,以期从无性生殖的角度,为探讨其濒危原因提供直观可靠的理论根据。结果显示:(1)中华水韭的大小孢子叶相间排列,无混生孢子囊。(2)隔丝为孢子供给营养,其体积直接影响孢子的大小、产量和育性。(3)大小孢子囊都近半数败育,小孢子囊为整齐发育,大孢子囊为不整齐发育。(4)大小孢子囊均无柄,且都不存在开裂结构,只有孢子囊壁腐烂后才能散播孢子。研究认为,中华水韭的濒危与孢子囊的发育特征密切相关,孢子囊的高频率败育、没有开裂结构以及对环境的依赖,是造成中华水韭濒危的重要因素之一;通过与近缘类群孢子囊的比较,发现仅水韭孢子的散播借助外力,对生境要求较高,即验证了水韭古老的系统学地位,同时说明水韭更具有监测生境地区环境指标的能力。     

The life histories in culture of the brown algae Gononema alariae sp.nov. and G. aecidioides comb.nov. from Greenland

Plants that agree with those provisionally referred to as Entonema alariae Jaasund (nom.prov.) have a direct type of life history. The swarmers from the plurilocular sporangia germinate and develop directly into new, small tufts. This development takes place under cold (4°C) as well as under warm (15°C) long day (LD) conditions in a medium with liver infusion. Erect, branched, uniseriate filaments develop in a medium without liver infusion. The laterals of these filaments are transformed to uniseriate, plurilocular sporangia under cold LD conditions. A lateral true hair has been observed on the erect filaments. Such filaments resemble those of the genus Gononema and the plant in question is, therefore, named Gononema alariae sp.nov. Ectocarpus aecidioides Rosenvinge = Entonema aecidioides (Rosenvinge) Kylin also has a direct type of life history. In a medium without liver infusion it occasionally develops erect filaments. These filaments also resemble those of the genus Gononema and the combination Gononema aecidioides (Rosenvinge) comb.nov. is, therefore, proposed.     

THE SPORANGIUM OF HORNEOPHYTON LIGNIERI (RHYNIOPHYTINA)

Numerous sporangia of Horneophyton lignieri from the Rhynie Chert locality in Scotland have been studied. The sporangia are branched, with two to four columellate lobes of varying length, and a continuous sporogenous zone or cavity occurs among the lobes. Unbranched sporangia, generally thought to be the typical form for the plant have not been found, and their presence is not established. Although not definitely proven, evidence suggests that the sporangia opened by means of a small apical pore or stoma. An area of thick-walled cells at the apex of each sporangial lobe probably played some role in this opening. Radial, trilete, azonate spores ranging from 39–49 μm in diam, with curvaturae perfectae are produced most commonly in tetrahedral tetrads and occasionally in isobilateral tetrads. Matters of spore preservation and possible ornamentation are discussed. The branched sporangia of this genus are unique among bryophytes and vascular plants and provide some evidence that certain synangia may have arisen from a single sporangium rather than from multiple sporangia borne singly at the tips of ultimate branches.     

DIMENSIONAL CORRELATIONS IN DEVELOPING SELAGINELLA SPORANGIA

With length of sporangia as a developmental index, the growth relationships of sporangia during differentiation were studied in strobili of Selaginella bigelovii. The strobili usually contain two rows of megasporangia and two rows of microsporangia with a mega- opposite a microsporangium at each node. Prior to the sporocyte stage a sporangium in a megasporangiate row is larger and elongates more rapidly than a sporangium opposite it at the same node in a microsporangiate row. The number of sporogenous cells is similar in sporangia of the same length from both rows until cell multiplication ceases in sporangia of the megasporangiate row, while it continues in sporangia of the same size in the microsporangiate row. The observed growth differences between sporangia of the micro- and megasporangiate rows are interpreted as events in the differentiation of two sporangial types.     

VALLITHECA VALENTIA GEN. ET SP. NOV., PERMINERALIZED SYNANGIA FROM THE MIDDLE PENNSYLVANIAN OF OKLAHOMA

Vallitheca valentia gen. et sp. nov. is a permineralized, synangiate fructification of probable seed fern affinities from the Wewoka Formation (Desmoinesian) near Ada, Oklahoma. Synangia are oblong to pyriform, average 1 cm long, and contain 32 to 48 tubular sporangia embedded proximally in ground tissue. The sporangia are arranged within the synangia in a unique pattern: a ring of peripheral sporangia dehisces toward the center of the synangium and a central group of sporangia dehisces outward. This unique arrangement is unlike that of any currently recognized group.     

Ultrastructural changes and a second mode of flagellar degeneration during ageing of Phytophthora palmivora sporangia.

Ageing of sporangia in Phytophthora palmivora is accompanied by a gradual breakdown of flagella, a transformation of the 'fingerprint' vacuoles, extensive vacuolization of the cytoplasm, accumulation of bundles of microtubules (mastigonemes)contained within cisternae of the rough endoplasmic reticulum, formation of a germination wall lining the inside of the sporangial wall and production of secondary sporangia. The mechanism of flagellar degeneration differs from that observed in directly germinating sporangia. In ageing sporangia and in sporangia induced to germinate directly with germ tubes, there is a close correlation between loss of competence for zoosporogenesis and breakdown of the flagella.     

CULTURE STUDIES ON REPRODUCTION OF SPERMATOCHNUS PARADOXUS (PHAEOPHYCEAE,CHORDARIALES)1

The life history of Spermatochnus paradoxus (Roth) Kütz. isolated from the Mediterranean Sea was studied in culture. Meiospores develop to a microscopic stage (microthallus) which at 20°C perpetuates asexually by plurilocular sporangia and formation of new microthalli. At 9°C microthalli act as homothallic gametophytes. Fusion of isogametes results in a diploid microthallus which, after differentiation of an apical cell, leads back to Spermatochnus plants. In addition, gametes develop without fusion to form haploid macrothalli, the further fate of which has not been determined. Chromosome numbers alternate between n = 20 ± 2 in the microthalli and 2n = 41 ± 4 in macrothalli.     

Secondary Sporangium Formation in Phytophthora Palmivora (Butl.) Butl

Very few sporangia of Phytophthora palmivora germinated directlyand produced secondary sporangia in distilled water and in solutionsof amino acids and carbohydrates at 30 °C. Although 1.0per cent (w / v) peptone and yeast-extract stimulated a highpercentage of germination by formation of germ tubes, less than1.0 per cent of the germinated sporangia produced secondarysporangia. Secondary sporangium formation was induced by transferringgerminated primary sporangia from a nutrient medium of sufficientlyhigh concentration to either distilled water or dilute solutionsof organic and inorganic compounds immediately after emergenceof the germ tubes. The percentage of germinated sporangia formingsecondary sporangia was influenced by both the nature and concentrationof the medium into which they were transferred. The secondarysporangia were significantly smaller than the primary sporangia. Phytophthora palmivora, germination, sporangium, Theobroma cacao L., cocoa     

Structurally preserved sphenophytes from the Triassic of Antarctica: reproductive remains of Spaciinodum

Permineralized cones found organically attached to Spaciinodum collinsonii stems are described from the early Middle Triassic silicified flora from the Fremouw Formation of Antarctica, and the species diagnosis is emended to include the reproductive specimens. The apical cones are organized into internodal and leaf-bearing nodal regions. Nodal septations span the central pith and cortex, and thin fimbrils subdivide the internodal areas into smaller chambers. The vascular system consists of 31-33 continuous bundles that do not alternate in position between successive nodes and internodes. Simple sporangia are associated with the cortical chambers and occur in one whorl on the axis. Spores are small, lack elaters, and have no discernible ultrastructure preserved, and they are interpreted to be immature. The Antarctic cones are different in structure from typical cones of modern and fossil members of Equisetales; however, they share similarities with some morphologically aberrant cones of extant Equisetum and several Late Paleozoic and Mesozoic compression-impression fossils. Spaciinodum is now the most complete anatomically described Mesozoic sphenophyte.     

MORPHOLOGY AND LIFE CYCLE OF A NEW CHYTRID WITH AERIAL SPORANGIA

An investigation of the life cycle of Caulochytrium gloeosporii Voos and Olive, a parasite of Gloeosporium, has confirmed the existence of an alternation of generations. Zoospores from sessile sporangia may develop vegetatively into similar sporangia or they may function as isogametes, fusing in pairs to produce cysts (zygotes) that give rise to slender-stalked aerial sporangia. Meiosis is believed to occur in the aerial sporangium, which at germination liberates eight asexual zoospores. The species is homothallic.     

Observations on Nothia aphylla Lyon ex Høeg

Naked branched axes associated with sporangia, originally described by Kidston and Lang (1920) as the probable fertile region of Asteroxylon mackiei, were later shown by Lyon (1964) to belong to an unknown plant which he named Nothia aphylla. The name was validated by Høeg in 1967. Nothia aphylla is described here in greater detail from new material collected from the Rhynie locality. The sporangia are lateral in terminal branched spikes. Their arrangement ranges from spiral to semiverticillate. The fertile axes terminate in clusters of 2–5 sporangia. The stalked sporangia are rather reniform with a distal transversely-extended dehiscence slit. Systematically Nothia has similarities to both Zosterophyllophytina and Rhyniophytina.     

BOTRYOPTERIS PINNULES WITH ABAXIAL SPORANGIA

Small sporangia borne abaxially on pinnules attached to Botryopteris foliar members are described from coal ball petrifactions of Early Pennsylvanian age. This is the first report of laminar sporangia in this genus. Sporangia are stalked and borne singly near lateral veins on Sphenopteris-like pinnules. Individual sporangia are of the leptosporangiate type, with a lateral annulus and a dehiscence zone of thin-walled cells immediately adjacent to the annulus. Spores are small, trilete, triangular in outline, typically have blunt spines covering the exine, and correspond to the dispersed spore genera Acanthotriletes, Leiotriletes, or Lophotriletes. These sporangia and their spores are unlike previously described globose Botryopteris fructifications from the Middle and Upper Pennsylvanian, but are similar to sporangia produced by modern members of the Osmundaceae.     

The pollen cones of Ginkgo from the Early Cretaceous of China, and their bearing on the evolutionary significance

A well-preserved pollen cone of the genus Ginkgo was found in the Yixian Formation (Early Cretaceous) of Liaoning Province, China, and is described as the new species Ginkgo liaoningensis . The pollen cone, catkin-like, consists of a main axis bearing scales at its base and spirally arranged sporophylls bearing 3–4 (−2) oval or elliptical sporangia. The sporangia are pendulous and dehiscent by a longitudinal slit. The mature pollen grains are monocolpate and elongate-elliptical, and the juvenile pollen grains are found in the tetrad stage. The characteristics of G. liaoningensis are very similar to those of the living Ginkgo biloba , but the sporophylls of G. liaoningensis bear 3–4 (−2) sporangia, whereas those of G. biloba bear mostly two sporangia. G. liaoningensis differs from fossil cones of Ginkgo huttoni from the Jurassic of Yorkshire, UK, and an unnamed specimen of Ginkgo from the Upper Cretaceous of Alberta, Canada, in the size and number of sporangia. The comparison between G. liaoningensis (fossil) and G. biloba (living) supports the reduction hypothesis of ovule organs in Ginkgo , with the number of sporangia having experienced the process of reduction from three or four to two since the Early Cretaceous.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 133–144.     

A reconsideration of Dimeripteris cornuta SCHWEITZER and CAI, a diminutive fossil plant from the Middle Devonian of Yunnan, China

Small plant fragments previously attributed to Dimeripteris cornuta SCHWEITZER and CAI and new specimens are described from the Middle Devonian (Givetian) Xichong Formation of Wuding, Yunnan Province, southwest China. A predominantly trifurcate branching pattern is recognized in lower orders of branching. Erect fusiform sporangia are borne in pairs terminally on a short pedicel on up to three times dichotomously-branching fertile unit. The beaked tips of the paired sporangia point outwards. This plant is distinguished from known plants by the trifurcate branching pattern and sporangia morphology, but is of problematic affinity. The plant is named Tauritheca cornuta (SCHWEITZER and CAI) WANG and BERRY nov. gen. and nov. comb.