Two species of Selaginella cones and their spores from the Bohemian Carboniferous continental basins of the Czech Republic

Two species of Selaginella cones from the Bohemian Upper Carboniferous continental basins of the Bolsovian and Westphalian D age are described, together with their in situ spores. Two specimens of Selaginella gutbierii yielded microspores closely comparable with the dispersed species Cirratriradites saturnii and megaspores closely comparable with the dispersed species Triangulatisporites vermiculatus. Microspores closely comparable with the dispersed species Cirratriradites annulatus and megaspores resemble the dispersed species Triangulatisporites tertius were isolated from cones of Selaginella cf. leptostachys. All the spores isolated from one cone are of the same type and would be referred to one dispersed micro- and megaspore species if found as Sporae dispersae. The paper contains a review of all palynologically studied Carboniferous Selaginella and Selaginella-like cones and reviews of all in situ and dispersed Cirratriradites and Triangulatisporites spores.     

<Emphasis Type="Italic">Isoetes eludens</Emphasis> (Isoetaceae), a new endemic species from the Kamiesberg,Northern Cape,South Africa

Summary   Isoetes eludens, a new, highly localised, endemic species from the Kamiesberg, Northern Cape is described. The aquatic species grows in a shallow temporary gnamma or !gau (rock pool) in Kamiesberg gneiss at an altitude of 1,284 m. It is characterised by a short, strongly 3-lobed stem, relatively short, and broad estomate sporophylls, a complete velum, the presence of an outer sporangium sack (a feature not previously reported for the genus), graphite-black, laevigate megaspores with a narrow, but tall laesura, microspores with near smooth proximal surfaces but with a papillate distal surface, the absence of a ligule and labium, and simple roots with few root-hairs. The systematic relationship of the species is difficult to determine as a result of convergent evolution in the genus. The sporangium sack does not support an affinity with any of the known species. Further surveys are needed to establish the geographical extent and conservation status of this remarkable local endemic.     

Ornamentation ofIsoetes (Isoetaceae, Lycophyta) microspores

More than any other taxonomic character, megaspores have been used in the genusIsoetes (known by the English common name of “quillwort”), despite the fallacy of a single-character taxonomy. Microspores, on the other hand, have been largely neglected in taxonomic schemes. Like megaspores, terms for microspore ornamentation (also known as “sculpturing”) have not been standardized. I examined microspore ornamentation, including both macroornamentation and microornamentation, of 52 taxa from Africa, Asia, Australasia, Europe, North America, and South America with the scanning electron microscope. Macroornamentation is discernible with light microscopy; microornamentation requires scanning electron microscopy. Ornately sculptured spores were much more frequent than were laevigate or psilate patterns: 21 taxa had an echinate pattern; 19 had an aculeate pattern; 6 were cristate; 5 were psilate; and 1 was laevigate. The proximal and distal ridges and surfaces may vary in both the type and density of ornamentation. Distinct macroornamentation patterns characterize certain species groups. Microornamentation types include granulate, bacillate, fimbriate, and filamentose: of the microspores I examined, virtually all were partially granulate; 11 were bacillate; 4 were fimbriate; and 1 was filamentose. Based on this limited sampling, species with a higher ploidy level often have larger microspores, but no clear relationship between microspore ornamentation and ploidy level was established, nor were any geographical or ecological trends clear. Like megaspores, microspore ornamentation is strongly convergent. Although microspores are often attached to megaspores, the role of spore ornamentation in coordinated dispersal remains unclear.     

Morphology and wall ultrastructure of some Middle Devonian dispersed megaspores from northern Poland

Specimens of dispersed Middle Devonian megaspores have been isolated from core samples from the Miastko 1 borehole in Western Pomerania. Comprehensive investigations using light, scanning and transmission electron microscopy supplement previous information on morphology and gross structure and provide data on spore wall ultrastructure of four megaspore species. Corystisporites acutispinosus is azonate; the inner layer is laminate, and the lumen is lined by a thick, laterally continuous lamina. The outer layer consists of small, tangentially aligned tabular elements that become wider, more extensive and irregularly arranged toward the outside. Coronispora variabilis is a coronate megaspore; the inner layer appears homogenous and is probably lamellate. The outer layer consists of elongate, cylindrical, branching elements that are overlaid within the proximal part of the body by a lamellate, compact, almost homogenous layer. Grandispora ciliata is pseudosaccate. The inner body is laminate with laminae thickening and becoming less continuous and less tightly packed toward the outside. The outermost region of the inner body and the innermost region of the outer envelope consist of tabular and cylindrical elongate units. The bulk of the outer wall is almost homogenous, and near the surface it is granular. Pomeranisporites subtriangularis is pseudozonate. The inner layer appears homogenous except for the presence of a single innermost lamina. The inner part of the outer layer may represent small tabular and cylindrical elements, and the outer part comprises folded laminae. The megaspores studied share numerous features of morphology and wall ultrastructure with the lycopsids, putative lycopsids, and some enigmatic Devonian plants.     

STUDIES ON FOSSIL AZOLLA: PRIMITIVE TYPES OF MEGASPORES AND MASSULAE FROM THE CRETACEOUS

Fossil Salviniaceae are described from the Claggett Shale and Judith River Formation, late Cretaceous (Campanian stage) of Montana. A new genus, Parazolla, from the Claggett Shale, has megaspores in which the swimming apparatus is composed of a number of elongate floats attached to the megaspore body and invested by coiled hairs. The floats separate at maturity. Massulae (bearing microspores) have simple hair-like glochidia, many of which are knobbed at their tips. Glochidia tend to resemble the perisporial hairs of the megaspore body. This resemblance provides fossil evidence of the homology of these two hair-like structures among living species of Azolla. In Azolla simplex from the Judith River Formation the megaspore has a single cap-like so-called columellate float. Massulae, which have anchor-shaped glochidia, are associated with these megaspores. A. simplex is the oldest species of Azolla and Parazolla the oldest member of the Salviniaceae so far found.     

ULTRASTRUCTURE OF DISPERSED AND IN SITU SPECIMENS OF THE DEVONIAN SPORE RHABDOSPORITES LANGII: EVIDENCE FOR THE EVOLUTIONARY RELATIONSHIPS OF PROGYMNOSPERMS

Abstract: The spore Rhabdosporites (Triletes) langii (Eisenack) Richardson, 1960 is abundant and well preserved in Middle Devonian (Eifelian) ‘Middle Old Red Sandstone’ deposits from the Orcadian Basin, Scotland. Here it occurs as dispersed individual spores and in situ in isolated sporangia. This paper reports on a detailed light microscope (LM), scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis of both dispersed and in situ spores. The dispersed spores are pseudosaccate with a thick walled inner body enclosed within an outer layer that was originally attached only over the proximal face. The inner body has lamellate/laminate ultrastructure consisting of fine lamellae that are continuous around the spore and parallel stacked. Towards the outer part of the inner body these group to form thicker laminate structures that are also continuous and parallel stacked. The outer layer has spongy ultrastructure. In situ spores preserved in the isolated sporangia are identical to the dispersed forms in terms of morphology, gross structure and wall ultrastructure. The sporangium wall is two‐layered. A thick coalified outer layer is cellular and represents the main sporangium wall. This layer is readily lost if oxidation is applied during processing. A thin inner layer is interpreted as a peritapetal membrane. This layer survives oxidation as a tightly adherent membranous covering of the spore mass. Ultrastructurally it consists of three layers, with the innermost layer composed of material similar to that comprising the outer layer of the spores. Based on the new LM, SEM and TEM information, consideration is given to spore wall formation. The inner body of the spores is interpreted as developing by centripetal accumulation of lamellae at the plasma membrane. The outer layer is interpreted as forming by accretion of sporopollenin units derived from a tapetum. The inner layer of the sporangium wall is considered to represent a peritapetal membrane formed from the remnants of this tapetum. The spore R. langii derives from aneurophytalean progymnosperms. In light of the new evidence on spore/sporangium characters, and hypotheses of spore wall development based on interpretation of these, the evolutionary relationships of the progymnosperms are considered in terms of their origins and relationship to the seed plants. It is concluded that there is a smooth evolutionary transition between Apiculiretusispora‐type spores of certain basal euphyllophytes, Rhabdosporites‐type spores of aneurophytalean progymnosperms and Geminospora‐/Contagisporites‐type spores of heterosporous archaeopteridalean progymnosperms. Prepollen of basal seed plants (hydrasperman, medullosan and callistophytalean pteridosperms) are easily derived from the spores of either homosporous or heterosporous progymnosperms. The proposed evolutionary transition was sequential with increasing complexity of the spore/pollen wall probably reflecting increasing sophistication of reproductive strategy. The pollen wall of crown group seed plants appears to incorporate a completely new developmental mechanism: tectum and infratectum initiation within a glycocalyx‐like Microspore Surface Coat. It is unclear when this feature evolved, but it appears likely that it was not present in the most basal stem group seed plants.     

ULTRASTRUCTURAL STUDIES OF IN SITU DEVONIAN SPORES: BARINOPHYTON CITRULLIFORME

Each sporangium in the Upper Devonian taxon Barinophyton citrulliforme contains both microspores and megaspores. Microspores range up to 50 μm in diam and possess a homogeneous sporoderm characterized by an outer separable layer. The sporoderm of the megaspores (up to 900 μm) is constructed of sporopollenin units that are loosely arranged in the outer portion of the wall, and that give the megaspore wall a spongy organization. Ultrastructural evidence suggests that the small spores were not abortive megaspores, but that both spore types were functional. The spores of this plant, as well as other Devonian spores that show less dramatic size differences, are suggested as demonstrating a phase in the evolution of heterospory where sex determination was established in spores within the same sporangium prior to the evolution of micro- and megasporangia.     

POROSTROBUS NATHORSTII SP. NOV.: A NEW SPECIES OF LYCOPSID CONE FROM THE EARLY PENNSYLVANIAN OF ILLINOIS

Thirty-one specimens of a small megasporangiate lycopsid cone referable to the genus Porostrobus Nathorst and abundant associated dispersed megaspores have been collected from Early Pennsylvanian strata in the Allied Stone Company quarry, Milan, Illinois. Based on other elements in the flora, the deposit is considered to be part of the Morrowan Caseyville Formation and probably of Namurian age. This is the first reported occurrence of Porostrobus in North America and the cones are recognized as a new species, P. nathorstii. The environment of deposition indicates that the cones may have been transported from the parent plant prior to preservation. Cones are preserved as coalified compressions measuring 15–36 mm long by 2.5–7 mm wide, and are characterized by an apical tuft of leaves up to 20 mm long. Sporophylls are spirally arranged on a narrow cone axis, lack a heel or keel, and have a long distal lamina. Sporangia contain a single functional megaspore tetrad. Mature megaspores are 750–1, 150 μm in diameter, have prominent trilete sutures raised to form a gula, and have numerous branched hairs confined to an equatorial band. Megaspores correspond to the dispersed form Setosisporites praetextus (Zerndt) Potonie and Kremp. Porostrobus nathorstii is the only species of the genus described to date that is monosporangiate.     

中国蹄盖蕨属植物孢子形态的研究

利用扫描电子显微镜对我国产蹄盖蕨属44种植物的孢子进行了观察。结果表明,该属孢子形态为单裂缝,两侧对称,极面观为椭圆形,赤道面观为豆形。外壁表面光滑,由周壁形成表面纹装饰。根据周壁的结构和表面纹饰,可分为两种类型;一是周壁外层发达,形成粗大的脊状纹饰,有11种属此类型;二是周壁外层很薄或不完全发育,由周壁内层或中层形成表面纹饰,有33种属此类型纹饰。本文还就本属的孢子形态特征以及与本属的属下分类关系、本属与邻近属的关系等进行了讨论。     

中国四种卷柏科植物孢子的形态观察

利用光学显微镜和扫描电子显微镜对睫毛卷柏（Selaginella ciliaris (Retz.) Spring）、甘肃卷柏（S.kansuensis Ching）、墨脱卷柏（S.mutensis Ching）、毛枝卷柏（S.trichoclada Alston）等4种中国产卷柏科（Selaginellaceae）植物的大、小孢子进行了详细的观察。结果表明,4种卷柏的大、小孢子在表面纹饰方面存在明显的差异,而在每一种内,孢子形态是基本稳定的。因此,孢子形态特征可以作为区分种的重要依据。4种卷柏的大、小孢子的孢壁多为混合纹饰类型,且近极面纹饰比远极面的细密。     

中国四种卷柏科植物孢子的形态观察

利用光学显微镜和扫描电子显微镜对睫毛卷柏(Selaginella ciliaris(Retz.)Spring)、甘肃卷柏(S.kansuensis Ching)、墨脱卷柏(S.mutensis Ching)、毛枝卷柏(S.trichoclada Alston)等4种中国产卷柏科(Selaginellaceae)植物的大、小孢子进行了详细的观察.结果表明,4种卷柏的大、小孢子在表面纹饰方面存在明显的差异,而在每一种内,孢子形态是基本稳定的.因此,孢子形态特征可以作为区分种的重要依据.4种卷柏的大、小孢子的孢壁多为混合纹饰类型,且近极面纹饰比远极面的细密.     

Spore morphology of Isoëtes (Isoëtaceae) from China

Micromorphological characters of mega- and microspores of five Isoëtes species from China were observed under scanning electron microscope (SEM). Megaspores of I. hypsophila have a levigate ornamentation, and are 358 µm in diameter (mean, n=30), microspores of this species have a gyrus ornamentation, and are 22 µm in length (mean, n=30); megaspores of I. yunguiensis have a cristate-reticulate ornamentation, with a size of 390 µm in diameter (mean, n=30), while microspores nearly smooth with some fine granulates, and with a size of 22 µm in length (mean, n=30); megaspores of I. taiwanensis are tuberculate and 312 µm in diameter (mean, n=30), echinate microspores are 24 µm in length (mean, n=30); cristate megaspores of I. sinensis are 409 µm in diameter (mean, n=30), and echinate microspores are 28 µm in length (mean, n=30); megaspores of I. orientalis have a cristate-reticulate ornamentation, with diameter of 420 µm (mean, n=30), microspores of this species have an echinate-tuberculate ornamentation with a size of 34 µm in length (mean, n=30). Based on the morphological characters of spores and chromosome numbers among taxa, it was found that mean spore size in each species of Isoëtes generally reflected the ploidy level. I. hypsophila, I. yunguiensis and I. taiwanensis, with smaller mean spore size, are diploidy with 2n=22; I. sinensis (2n=44) and I. orientalis (2n=66), with larger mean spore size, are polyploidy. The spore morphology of Isoëtes still plays an important role in identification and classification of Isoëtes from China.     

THE ANATOMY OF CALLOCARDIA HUNGERFORDI (BIVALVIA: VENERIDAE) AND THE ORIGIN OF ITS SHELL CAMOUFLAGE

Callocardia hungerfordi (Veneridae: Pitarinae) lives in subtidalmuds (220 to 240m C.D.) and is covered by a dense mat of mudthat, effectively, camouflages the shell. The periostracum is two layered. The inner layer is thick andpleated, the outer thin and perforated. From the outer surfaceof the inner layer develop numerous, delicate (0.5 mm in diameter),calcified, periostracal needles. These penetrate the outer periostracum.Mucus produced from sub-epithelial glands in the inner surfaceof the mantle, slides over the cuticle-covered epithelium ofthe inner and outer surfaces of the inner fold and the innersurface of the middle mantle fold to coat the outer surfaceof the periostracum and its calcified needles. Increased productionat some times produces solidified strands of mucus which bindmud and detrital material into their fabric to create the shellcamouflage. Calcified periostracal needles have been identified in othervenerids, including some members of the Pitarinae, but how theyare secreted and how the covering they attract is producedand, thus, how the whole structure functions, has not been explained. (Received 7 December 1998; accepted 5 February 1999)     

棉花751与多父本杂交受精细胞学研究及性状分析

本文报导了以棉花７５１为母本与鸡脚叶棉、乌干达棉、红叶棉、汉寿大桃、草棉等５个父本的混合花粉进行杂交。授粉后,观察了７５１大小孢子和雌雄配子体的发生、发育及其受精过程。切片观察表明在大小孢子的发生、发育与花蕾大小成正相关。大小孢子的发生在减数分裂前是不同步的。小孢子的发生早于大孢子发生１￣２个时期。减数分裂后它们的发育逐渐趋向同步。开花时达到同步成熟。用多父本的混合花粉授粉,其受精过程仍为单精入卵     

A NEW SPECIES OF MARSILEA FROM THE DAKOTA FORMATION IN CENTRAL KANSAS

Discovery of compression/impression megafossil material from the Cenomanian (mid-Cretaceous) in Kansas documents the occurrence of the genus Marsilea during this age. Only vegetative material has been found as complete plants; associated structures that may be fertile structures could belong to the genus also. This new fossil species extends the megafossil record of the genus back to the mid-Cretaceous when previously only megaspores attributed to the family occurred during this time. The fossil record of the heterosporous aquatic fern families is reviewed with emphasis on the Marsileaceae.     

A new genus and species of heteronemertean from the Changjiang (Yangtze) River Estuary

A new genus and species of heteronemertean, Yinia pratensis gen. nov. and sp. nov., collected from low salinity waters (salinity 0.2–0.4 ‰) at Changjiang River Estuary, is described and illustrated. The species possesses a proboscis with an outer circular and an inner longitudinal muscle layer, and is placed in family Lineidae sensu Gibson. The following combination of morphological features distinguishes the new species from any other genera in this family: proboscis with two muscle crosses; dermis without connective tissue layer between gland cells and body wall outer longitudinal muscle layer; rhynchocoel wall circular muscles not interweaving with adjacent body wall longitudinal muscles; foregut with circular somatic muscles and subepithelial gland cell layer; neurochord cells present in central nervous system; caudal cirrus missing; blood system developed into alimentary plexus extending almost the full length of the body. Another significant character is that the lobular excretory cells are extremely well developed which may represent adaptation to water of low salinity. This revised version was published online in July 2006 with corrections to the Cover Date.     

甘蔗雌雄蕊的解剖学研究

甘蔗雄蕊花药的壁由四层细胞构成,药室内壁在花药成熟时才发育。花粉母细胞减数分裂属连续型,四分体正常发育为小孢子,但当开花时,只有少数进一步发育为成熟的花粉粒。甘蔗雌蕊柱头是分枝的,每一柱头毛是由数个细胞质浓密的细胞,呈不规则的纵列而组成。倒生胚珠一个,着生于子房室的内侧;内、外珠被均由两层细胞构成,外珠被上侧未能生长到珠孔,内珠被的内层细胞在胚珠发育中不断增大体积。石蜡制片是以樟油为透明剂的。     

Diversity of exine structure in Upper Carboniferous (Westphalian) selaginellalean megaspores

Studies of wall structure in Mesozoic and Recent selaginellalean megaspores have been well documented. However, Palaeozoic examples have received minimal attention. The principal Palaeozoic megaspore genus of likely selaginellalean affinity is Triangulatisporites, extending from the Upper Devonian to the Upper Carboniferous. The particulate wall ultrastructure of a previously published Carboniferous (Duckmantian) megaspore assigned to this genus suggested that this form of wall construction may have been the ancestral wall structure of the group, an observation which posed difficulties in relating selaginellalean ultrastructure to that of other contemporaneous lycopsid megaspores. Subsequent investigation showed that the genus also contains more laminate exines similar to those of other extinct lycopsids and extant Selaginella species. Our new examples of Triangulatisporites ultrastructure from the Langsettian, Duckmantian and Westphalian D yield more information regarding early variation of wall structure within Carboniferous selaginellalean megaspores and suggest that a more laminate wall composition is at least as old as the particulate form. However, without further investigation of Lower Carboniferous forms, we are unable to state which is indeed ancestral. The laminate structure reported here and elsewhere is, none the less, more easily related to comparable ultrastructure in other groups of Carboniferous lycopsid megaspores and could suggest a link with such genera as Zonalesporites and early Lagenicula. This would be in keeping with current concepts regarding the most primitive ultrastructural type within lycopsid megaspore walls.     

ARIADNAESPORITES AND GLOMERISPORITES IN THE LATE CRETACEOUS: ANCESTRAL SALVINIACEAE

Glomerisporites and Ariadnaesporites are two genera based on megaspores and microspores from the late Cretaceous. Each has megaspores with characteristics shared with other late Cretaceous Salviniaceae, including numerous floats, an acrolamella, and a complex perispore. Microspores are borne singly, however, not in characteristic salviniaceous massulae. Microspores of Glomerisporites have a pseudovacuolate basal region and a single spore in an apical neck. Microspores of Ariadnaesporites are structurally like the megaspores but of smaller size. Ariadnaesporites varius occurs in the Cenomanian Stage (early late Cretaceous) and is the oldest presumed member of the Salviniaceae.     

Fossil plants with spores in the sporangia from the Upper Devonian (Frasnian) deposits of northern Timan

Fossil plants from the Upper Devonian (Frasnian) of northern Timan are studied. The sporangia contain well-preserved spores, which were studied in transmitted light using a scanning electron microscope. The genus Gutzeitia S. Snigirevsky, gen. nov. is established. Macroremains and in situ spores of G. timanica (Petros.) S. Snig., comb. nov. and ?Cephalopteris mirabilis (Nath.) Nath. are described. Microspores in Dimeripteris gracilis Schmalh. are identified, and microspores and megaspores in ?Cephalopteris mirabilis are studied for the first time.