Permanent dyads in sporangia and spore masses from the Lower Devonian of the Welsh Borderland

Dyads, interpreted as cryptospore permanent dyads, are reported from sporangia and spore masses recovered from fluviatile deposits of Lochkovian (Early Devonian) age from the Welsh Borderland. The morphology, anatomy and ultrastructure of the specimens have been analysed using LM, SEM and TEM. Two specimens consist of a single sporangium terminating an axis: one is cup-shaped and attached to an unbranched axis and named Culullitheca richardsonii gen. et sp. nov., the other comprises an isotomously branching axis with one sporangium preserved and is named Fusitheca fanningiae gen. et sp. nov. Two specimens show dyads adhering to cuticular fragments presumably derived from sporangia. In one the cuticle is of irregular shape, in the other it is elliptical. The final specimen comprises an elongate spore mass. In all cases ultrastructural analysis reveals that the spore walls are essentially homogeneous. Our findings suggest that cryptospore permanent dyads were produced by rhyniophytoid plants of small stature. The affinities of these plants remain conjectural, as is the relationship of the cryptospore permanent dyads with other sporomorph morphotypes (cryptospores and trilete spores). However, the production of dyads by a plant with a bifurcating sporophytic axis is evidence against affinity with extant bryophytes. The mode of formation, adaptive significance, affinities, phylogenetic relationships and stratigraphical history (including demise) of cryptospore permanent dyads is discussed.     

华北泥河湾盆地植被、气候与早期人类生存环境研究进展

中国北方泥河湾盆地可以与非洲奥杜威峡谷相媲美,它们具有十分相似的地质演化过程,这里河湖相沉积发育,并且蕴藏着丰富的古生物化石和大量古人类遗迹,是研究东亚早期人类生存环境变化的重要区域。基于前人积累的晚上新世以来植被、气候及早期人类生存环境的大量研究资料,经分析发现在大约2.6Ma(百万年),泥河湾盆地的植被由阔叶林转变为以针叶林为主;大约1.92 Ma以后,植被以温带森林-草原(主要是松属、蒿属及藜科)/温带草原(主要是蒿属和禾本科等)为主。通过对比发现,晚上新世以来中国北方从西部到中部,由森林转变为以森林-草原为主的植被类型出现的时段呈现明显的阶梯型。此外,泥河湾盆地气候出现了13个冷暖旋回, 15个干湿旋回,显著的冷干事件发生在2.8 Ma、2.6 Ma、1.92 Ma及143.8 ka (千年),湿润事件发生在43、32和6.6 ka。早期人类生活在森林-草原或以草原为主的植被环境中,气候冷暖干湿波动较大,水源丰富,大量哺乳动物共存。建议在建立泥河湾人类遗址更为精细地层的年代框架下,开展古气候温度与降水参数的定量化研究,将有助于精准重建古人类生存环境及揭示其变化规律。     

Spore Composition in a Garbage Disposal Plant

The municipal garbage disposal plant in Turku converts all household garbage into ash by burning it in specially constructed ovens. For several years, the workers there have been complaining of allergy and skin diseases. An investigation was started in January, 1977, to determine the frequencies of pathogenic and allergenic fungi in the air inside this plant. The survey is being made four times during 1977 (two of these have already been carried out), using both Petri dish method and Hirst-Burkard traps. The spore trap collections indicate that the seven sampling sites can be classified into three groups with regard to spore frequencies: (1) the dumping room and the room for crushing the wastes show extremely high frequencies (170 000-180 000 spores/m³), with Penicillium and Aspergillus as the main spore types. (2) In the furnace unit the frequencies are clearly higher than in normal indoor air (over 10 000 spores/m³). (3) In the washing, dressing and control rooms the frequencies are about the same as in the indoor air in general, or even lower. The Petri dish collections gave similar results; e.g. the concentrations of Penicillium and Aspergillus in the dumping room are 6000-fold when compared with the outdoor air. The wide variations in the spore contents are directly correlated with the kind of garbage under treatment. The outdoor air collected at a distance of c. 200m showed no conspicuous differences when compared with the air in Turku in general. These results indicate that it is absolutely necessary to use face masks—at least in the dumping room conditions.     

A new species of Baragwanathia from the Sextant Formation (Emsian) Northern Ontario, Canada

Baragwanathia abitibiensis is described from the Sextant Formation of northern Ontario, Canada (middle to upper Kmsian age). The plant remains are primarily compressions in which flattened xylem strands, epidermis with stomata, and cuticle are well preserved. Pyrite permineralization of the leaves was Ibiuid in one specimen. Comparison with B. longijolia Lang & Cookson indicates remarkable morphological similarities and probable anatomical similarities although details of the structure of the epidermis and cuticle are lacking in B. longijolia. No information is available on the outline of the cauline xylem strand in B. abitibiensis nor on the form and position of the sporangia it bore. Comparisons are also made to species of Drepanophycus. The age of/?, longijolia and the Baragwanathia Flora, is discussed with particular reference to the putative dating of some specimens as Silurian. The morphological and anatomical complexity of Baragwanathia is at a level of advancement typical of Early to Middle Devonian lycopods. There is no evidence of precursors to the genus associated with the fragments of land vascular plants in the well-dated Silurian sediments of Wales, Czechoslovakia, New York State, or Podolia.     

Palynology: A useful tool in understanding palaeoclimatic changes through the Pliocene-Pleistocene from the deep offshore Niger Delta,Nigeria

Recent global ecological problems have necessitated more research into past environments so that accurate comparisons between past and present climatic conditions can be established and projections made for the future. In order to achieve this, palynological data from Well-C from the deep offshore (> 200 m) Niger Delta region were employed in an attempt to reconstruct the Late Pliocene-Pleistocene palaeoclimate. Four informal palynofloral assemblage zones (PAZ) I–IV are defined and correlated with four major cycles of alternating dry and wet climatic conditions. Within the major cycles, savanna and montane pollen assemblages became dominant in the late-Pliocene and mid-Pleistocene, while mangroves, brackishwater swamp, freshwater swamp and lowland rainforest prevailed during the early- and late-Pleistocene. The palaeoclimate of the late Pliocene and mid-Pleistocene was relatively colder and drier, with alternating relatively warmer and wetter conditions in the early and late Pleistocene, respectively. The pollen data from Well-C showed periods of climatic change during Late Pliocene-Pleistocene times, while the periods of climatic change revealed by pollen data from Lake Tilla, NE Nigeria, during Holocene times ranged from ∼2.0 to ∼3.8 Ka. Therefore, the cyclicity of climate change during Upper Pliocene-Pleistocene time is far greater than that of Holocene times. Our palaeo-climatic reconstruction conflicts with those that indicate predominantly dry climatic conditions in the Niger Delta region during the Pliocene-Pleistocene. The reconstructed palaeoclimate in this study can help to compare the past climatic conditions to that of the present and perhaps serve as a basis for studies of future climatic change.     

LYCHNOTHAMNUS BARBATUS(轮藻植物)的生态与保护研究

轮藻植物属Lychnothamnus(Rupr．)Leonh．自晚始新世即有化石代表,在上新世繁盛且分布广泛,此后分异度降低、分布范围缩减,延续至今仅存1种：L．barbatus(Meyen)Leonh．。上世纪末叶前该种还曾广泛分布于欧洲、印度、中国、巴布亚新几内亚和澳大利亚,而后该种在澳大利亚曾经留有记录的产地消失,直到1996年才被再次发现。本文描述了澳大利亚L．barbatus的居群特征,包括植株、卵囊球和藏卵器形态特征以及萌发生态学的实验研究结果。讨论该种的野外生态学、共生种、全球范围的分布与丰度特征,探讨该种衰落的原因并提出植物保护方案。     

环境胁迫对库拉索芦荟叶片超微结构影响研究

对1年生库拉索芦荟分别用盐(1.8%的NaCl)、低温(10℃)、干旱[25%(w/v)的聚乙二醇-6000]3种胁迫条件处理7d后,对其叶肉细胞超微结构进行观察.结果发现:3种胁迫处理均可使库拉索芦荟细胞膜系统、叶绿体、线粒体、细胞核等结构受到不同程度的破坏,叶绿体周围出现许多小泡,导致细胞内膜系统紊乱,细胞器结构稳定性降低;盐胁迫下高尔基体在细胞质中解体;盐和低温胁迫下均可见线粒体膜与叶绿体膜发生融合、线粒体嵌在叶绿体当中的现象.另外,本研究发现,盐胁迫、低温胁迫比干旱胁迫对库拉索芦荟细胞膜的损伤更严重,而水分胁迫对其的伤害程度较小,表明库拉索芦荟的抗旱性较其抗盐性更强.     

Betulaceous leaves and fruits from the British Upper Palaeocene

Fossil leaves and bracteate fruits are described from a new Upper Palaeocene locality in the Reading Beds near Newbury, southern England. The leaves are assigned to Craspedodromophyllum acutum Crane and correspond in many respects to those of living Betulaceae. The bracts and fruits are assigned to Palaeocarpinus laciniata Crane, which although referable to the Coryleae exhibits a novel combination of the characters of several living genera, particularly Corylus and Carpinus. An argument is presented for the association of these organs as a reconstructed fossil plant which is an extinct member of the Betulaceae. The evolution and fossil record of the Betulaceae are discussed, the late Upper Cretaceous and Palaeocene being regarded as the time at which the characters of modern genera were beginning to differentiate. Carpinus appears to have undergone a major Eurasian diversification during the late Palaeogene and early Neogene. Dispersal in Palaeocarpinus laciniata was probably less specialized than in most extant Coryleae.     

Ultrastructure of some Cambrian palynomorphs from the Bright Angel Shale, Arizona, USA

Palynomorphs with complex resistant walls have been recovered from several Cambrian deposits in the continental United States. Those recovered from the Bright Angel Shale of Arizona typically preserve both a primary wall, and an outer envelope (synoecosporal wall) that encloses multiple spore-like bodies within. At least three distinct types of primary walls, are recognized with the TEM: 1) a unilaminate wall with a smooth inner surface and a sculptured outer surface, 2) a wall of three unornamented laminae of very uniform thickness, and, 3) a thicker wall with multiple thin, lightly-staining layers embedded in a darker matrix. This third type of primary wall bears a strong resemblance to those of certain Lower Devonian hilate cryptospore monads from the Welsh Borderlands. No extant algae produce spores with walls as thick or as complex, suggesting that these Cambrian palynomorphs were the desiccation-resistant spores of cryptogams belonging to the charophyte–embryophyte lineage. Multilaminate spore walls, which are characteristic of some extant liverworts and Paleozoic cryptospores, may have evolved via the fusion of separate, multiple laminae. This appears to be the primitive plant sporoderm type, but it may have evolved asynchronously with respect to the evolution of the embryophytic development of the sporophyte in land plants.     

Fossil angiosperm wood: its role in the reconstruction of biodiversity and palaeoenvironment

Fossil wood is subject to different taphonomic, sampling and recognition biases in the palaeobotanical record when compared with leaves and palynomorphs. Wood therefore provides a systematically independent source of information that can increase our knowledge of past biodiversity and environments. Increase in fossil wood records from Cretaceous and Tertiary sediments helps further the understanding of trends in anatomical specialization through geological time. These data can then be used to distinguish such specialization from anatomical response to environmental change. Two case studies, a Late Cretaceous early Tertian' wood flora from Antarctica and a lower Tertiary w ood flora from southern England, have been used to exemplify the importance of studying the fossil wood component of palaeofloras.     

Paleolimnological investigations in humid and arid zones of the Soviet Union

There are many lake basins in the Soviet Union, both in the humid and the arid regions, including lowland and alpine, and shallow and deep-water lakes. Lithological, geochemical, radiological and paleobiological methods have been utilized in studying the history of these lakes. Lake Zaisan in Kazakhstan is described as an example of lake development in the arid zone, whilst the lake systems of the Pribaltica, where human influence on the environment is clearly recorded, exemplifies the humid zone.     

Pollen morphology of Gontortae (Acanthaceae)

Variation in pollen morphology is described and illustrated for 36 genera of Acanthaceae with contorted corolla aestivation. A parsimony analysis of pollen characters is presented.