ULTRASTRUCTURE OF THE RED TIDE DINOFLAGELLATE GYMNODINIUM BREVE. I. GENERAL DESCRIPTION1,2,3

Gymnodimium breve Davis, an unarmored marine dinoflagellate has a cell covering (theca) composed of four membranes. The inner two membranes represent a vesicular layer and in tangential section, the theca appears composed of polygonal areas. Unusual threat ridges are located in the cingular region between the epi- and hypocone. This osmotically sensitive species is extremely vesiculate with dispersed areas of cytoplasm containing typical eukaryotic organelles as well as other organelles found only in dinoflagellates. The non-vesiculated cytoplasm is continuous in serial sections. The chloroplasts can contain either quasi-radial or parallel lamellae typically consisting of three thylakoids each. The pyrenoid is multiple-stalked and lacks a starch cap. The dinophycean pusule is simple and similar to those found in several unarmored marine species. The nucleus is typically dinophycean but the chromosomes appear to lack nonfibrillar material.     

THE ULTRASTRUCTURE OF LICHENS. II. CLADONIA CRISTATELLA: THE LICHEN AND ITS ISOLATED SYMBIONTS1,2,3

A Comparative Study Was Made Of The Fine Structure of Cladonia Cristatella and its algal Symbiont Trebouxia Erici in their lichenized and cultured ( nonlichenized) states. Pyrenoglobuli were produced by the alga in the symbiotic and free conditions. Starch was formed during hydrated conditions. Pyrenoglobbuli migrated to the outer parts of the pyrenoid only during dry periods. Dictyosomes and eyespots were observed for the first time in Trebouxia. The pyrenoid divided by fragmentation. Ellipsoidal bodies were common in the hyphae of the lichenized fungus and absent in cultured hyphae, except for 1 colony which had been induced to form pycnidia. The ellipsoidal bodies were associated closely with the internal membrane system of the mycobiont. Haustoria seemed to penetrate the algal cells by enzymatic digestion. Intrahyphal hyphae were common.     

ULTRASTRUCTURE OF THE DINOFLAGELLATE PERIDINIUM CINCTUM F. OVOPLANUM. I. VEGETATIVE CELL ULTRASTRUCTURE

Vegetative cells of Peridinium cinctum f. ovoplanum have a dense cytoplasm containing those organelles characteristic of eukaryotic cells. Thecal plates have a fibrillar substructure with numerous 200-nm pores. Chloroplasts are radially arranged and contain a simple internal pyrenoid. An eyespot is associated with the chloroplast. The large, centrally located nucleus contains over 100 chromosomes dispersed in a granular nucleoplasm. Chromosomal bands with a periodicity of 86 nm are present perpendicular to the long axis of the chromosome. Numerous chromosomes are attached to the nuclear envelope. Peridinium cinctum vegetative cell morphology is compared to other dinoflagellates examined.     

AN EXPANDED SURVEY OF THE ULTRASTRUCTURE OF RED ALGAL PIT PLUGS1

The fine structure of pit plugs in 90 species of red algae was examined, bringing the total number of species in the continuing survey to 153. The organization of plug caps was confirmed to be a stable, predictable trait within thalli, between generations in heteromorphic life histories, and within the presently recognized orders, with one exception—the Acrochaetiales. Two forms of the outer cap were found in this group, a thin plate, as in the Nemaliales and Palmariales, and a dome, as in Batrachospermales and Corallinales. Variation of pit plug structure indicates that the Acrochaetiales are a heterogeneous assemblage and that pit plugs will be useful in reappraising their systematics. The systematic affinities of several species of uncertain affinities are clarified. Schmitziella endophloea Bornet et Batters is excluded from both orders, Corallinales and Acrochaetiales, with which it previously was allied. Although other ordinal attributions are not precluded by pit plug structure alone, pit plug structure is consistent with placement of Apophlaea sinclairii Harvey and Hildenbrandia rivularis (Liebman) J. Agardh in the Hildenbrandiales, Plagiospora gracilis Kuckuck, Schmitziella endophloea, and Wurdemannia miniata (Duby) J. Feldmann et Hamel in the Gigartinales, and Pseudorhododiscus nipponicus Masuda in the Palmariales.     

THE ULTRASTRUCTURE OF MOUSE LUNG GENERAL ARCHITECTURE OF CAPILLARY AND ALVEOLAR WALLS

The general architecture of capillary and alveolar walls of the mouse lung was studied by means of the electron microscope. In order to minimize tissue damage and to improve the cutting properties of embeddings, several modifications in the tissue processing methods were adopted. These modifications were: fixation by infusion, a prolonged time of dehydration, of impregnation, and of polymerization, the use of acetone for dehydration, ammonium sulfide treatment of the fixed and washed tissue, and an elevated (80°C.) polymerization temperature combined with the use of prepolymerized methacrylate. The generally favorable effects of these modified methods upon preservation and cutting properties of embedded tissue are discussed. Both capillary endothelium and alveolar epithelium were found continuous and without pores. The endothelium was seen to be thinnest in those portions that were adjacent to alveolar air spaces. Two morphological "types" of alveolar epithelial cells were found. One protruded into the alveolar lumen with its thick portion containing the nucleus. The other was often located in a niche of the alveolar wall, and contained peculiar dark inclusions amidst numerous mitochondria. Both were attenuated at their periphery to form the thin epithelial layer. The layer between endothelium and epithelium was designated as basement membrane. It was seen to be generally thin and structureless, but was found thickened in some areas where it also contained collagen fibrils.     

THE ULTRASTRUCTURE OF PALEOZOIC FERN SPORES: I. BOTRYOPTERIS

The spores of four species of the Paleozoic filicalean fern Botryopteris are examined at the ultrastructural level. Spores of B. cratis, B. forensis, B. globosa, and an unnamed species from the Lower Pennsylvanian, are compared on the basis of sporoderm stratification and the presence or absence of a sculptine layer. The species examined differ widely as to the type of reproductive unit in which they are borne and include forms that range throughout the Pennsylvanian. In all species the exine is homogeneous, lacking cavities and lamellae. A thin nexine is present in the Middle and Upper Pennsylvanian taxa, but is absent in the Lower Pennsylvanian spores. Only one spore type (B. cratis) possesses a clearly defined sculptine layer. Features of the sporoderm are compared with those of extant, homosporous pteridophyte spores.     

THE ULTRASTRUCTURE OF THE CAT MYOCARDIUM : I. Ventricular Papillary Muscle

The ultrastructure of cat papillary muscle was studied with respect to the organization of the contractile material, the structure of the organelles, and the cell junctions. The morphological changes during prolonged work in vitro and some effects of fixation were assessed. The myofilaments are associated in a single coherent bundle extending throughout the fiber cross-section. The absence of discrete "myofibrils" in well preserved cardiac muscle is emphasized. The abundant mitochondria confined in clefts among the myofilaments often have slender prolongations, possibly related to changes in their number or their distribution as energy sources within the contractile mass. The large T tubules that penetrate ventricular cardiac muscle fibers at successive I bands are arranged in rows and are lined with a layer of protein-polysaccharide. Longitudinal connections between T tubules are common. The simple plexiform sarcoplasmic reticulum is continuous across the Z lines, and no circumferential "Z tubules" were identified. Specialized contacts between the reticulum and the sarcolemma are established on the T tubules and the cell periphery via subsarcolemmal saccules or cisterns. At cell junctions, a 20 A gap can be demonstrated between the apposed membranes in those areas commonly interpreted as sites of membrane fusion. In papillary muscles worked in vitro without added substrate, there is a marked depletion of both glycogen and lipid. No morphological evidence for preferential use of glycogen was found.     

STUDIES OF A MARINE GRASS,THALASSIA TESTUDINUM. I. ULTRASTRUCTURE OF THE OSMOREGULATORY LEAF CELLS

Thalassia testudinum (Turtle Grass), a marine monocot which grows completely submerged, differs from intertidal and other halophytic angiosperms in that it has no specialized saltsecretory glands. Osmoregulation appears to be accomplished by the epidermal leaf cells which have highly invaginated plasmalemmas with numerous mitochondria situated in the interdigitations. The ultrastructure and proposed mode of secretion are similar to that of the salt-marsh monocot Spartina, but differ from that found in dicots. Evidence is presented to show why monocots are the only angiosperms which have adapted to a completely marine environment.     

松毛虫属(Dendrolimus Germar)在中国东部的地理分布概述

我国的松毛虫种类已知的有13种, 是世界上已记载的松毛虫种类最多的国家。 根据中国科学院动物研究所历年来在国内所收集的松毛虫种类和分布的资料, 结合已知主要松树种类的天然分布进行综合分析的结果, 显示出松毛虫不同种类的地理分布与其寄主植物的天然分布有着密切的相关。例如西伯利亚松毛虫的分布只限制在东北地区兴安落叶松、黄花松的天然分布范围里, 油松毛虫在油松分布区, 赤松毛虫在赤松分布区, 云南极毛虫在云南极分布区以及马尾松毛虫在马尾松分布区等。 由于这些松树种类彼此间的天然分布界限十分明显而基本上少有重迭, 因此试将我国东部地区松毛虫不同种类的地理分布按照其寄主植物划分为以下三个部分、五个松毛虫区: 一、东北部分 北界大兴安岭, 南至安东—沈阳线(相当于全国一月份平均-12℃等温线), 是西伯利亚松毛虫主要分布区, 也是兴安落叶松和黄花松天然分布所在地。故名1)西伯利亚松毛虫区。 二、华北部分 北界西伯利亚松毛虫区, 南至淮河流域(相当于全国一月份平均0℃等温线), 是油松毛虫和赤松毛虫主要分布区, 也是油松和赤松的主要分布所在。因此可分为2区: 2)油松毛虫区 主要位置在冀热山地和黄土高原东部, 是油松毛虫分布区, 是油松分布所在地。 3)赤松毛虫区 主要位置在山东半岛、辽东半岛、渤海湾沿岸, 最南直到苏北连云港, 是赤松毛虫分布区, 也是赤松和黑松的主要分布所在地。 三、华南部分 北界油松毛虫和赤松毛虫区, 南至南海沿岸, 东到台湾, 西至昌都、波密。松毛虫种类较多, 有马尾松毛虫、云南松毛虫、思茅松毛虫、西昌松毛虫等。松树种类有马尾松、云南松、思茅松等。从中又可分为2区: 4)马尾松毛虫区 占华南的绝大部分, 东至台湾, 西至大相岭东坡, 西南至贵州毕节, 是马尾松毛虫分布区, 也是马尾松分布所在地。 5)云南松毛虫区 主要在四川西部和云南省境内, 是云南松毛虫、西昌松毛虫和思茅松毛虫主要分布区, 也是云南松、思茅松分布所在地。 以上划分不仅可供各地识别松毛虫种类或采取防治时之参考, 而且还可以为进一步发现新的松毛虫种类和探索种下问题以及发生规律研究等提供一些新的线索。     

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.