MORPHOLOGY AND FINE STRUCTURE OF FISCHERELLA AMBIGUA1

Fischerella ambigua is a branching blue-green alga, the filamentous nature of which is maintained almost entirely by sheath material. Cell division in this organism most closely resembles the septal division found in most unicellular organisms. In all filamentous blue-green algae previously examined with the electron microscope, cell division has resulted from the imagination of the plasma membrane and inner wall layer only; both the middle wall and the outer wall layers remain continuous throughout the length of the filament. In Fischerella, by contrast, the plasma membrane and the inner wall layer invaginate to produce initially 2 cells. However, the middle wall layer, outer wall layer, and sheath also invaginate to separate the daughter cells. The sheath alone remains continuous throughout the length of the filament.     

硬蜱盾窝与盾窝腺的细微结构

用扫描及透射电镜研究硬蜱盾窝与盾窝腺的结构.幼蜱只有横缝状盾窝原基,盾窝腺尚未发育;若蜱盾窝增大,其孔数相应增加;到成蜱阶段,不仅盾窝增大,而且盾窝腺完成发育.对9种雌蜱盾窝进行比较,在其大小和孔数方面有一定差别.亚洲璃眼蜱雄蜱盾窝腺不发达,几个叶瓣贴在一起,组成1—2个腺体组.雌蜱吸血前,叶瓣相互贴在一起.吸血后,球状叶瓣散开,连接叶瓣的导管清楚可见,分泌细胞中颗粒增多,这与其分泌性信息素有关.     

FINE STRUCTURE OF THE ZYGOTE AND EARLY EMBRYO IN QUERCUS GAMBELII

This investigation begins with the late zygote and traces ultrastructural development to the late globular stage of the embryo. Two nucleoli and satellite nucleoli sometimes occur in the zygote nucleus. Mitochondria, dictyosomes, cytoplasmic ribosomes, rough ER, and lipid bodies are numerous in the zygote. Microbodies are occasionally seen. The cell wall becomes well developed before the first division. No plasmodesmata occur in the zygote wall. The basal cell of the proembryo and the suspensor cells of the later embryo have very dense cytoplasm with a high concentration of cytoplasmic ribosomes. The nuclei are very electron opaque. The terminal cell and the cells of the embryo proper have a fine structure similar to that of the zygote. Plastids increase in number, size, starch content, and amount of thylakoid lamellae as the embryo develops. Mitochondria are numerous and appear active at all stages. Dictyosome activity, ribosomal aggregation, and the amount of ER are highest during the late globular stage. Lipid bodies are present up to the early globular stage, then disappear. The inner cell walls of the embryo are thin and have many plasmodesmata. These walls begin to thicken at the late globular stage, and at this time the size of the embryo begins to show an increase over that of the zygote. The results show a corresponding increase in the amount and activity of the metabolic machinery as the development of the embryo progresses. Lipids are probably more important as a nutrient source in the zygote and early embryo; starch becomes more important in the late stages. Absorption of nutrient material into the embryo sac and developing embryo appears to be from the chalazal end.     

FLAGELLAR MOTION AND FINE STRUCTURE OF THE FLAGELLAR APPARATUS IN CHLAMYDOMONAS

The biflagellate alga Chlamydomonas reinhardi was studied with the light and electron microscopes to determine the behavior of flagella in the living cell and the structure of the basal apparatus of the flagella. During normal forward swimming the flagella beat synchronously in the same plane, as in the human swimmer's breast stroke. The form of beat is like that of cilia. Occasionally cells swim backward with the flagella undulating and trailing the cell. Thus the same flagellar apparatus produces two types of motion. The central pair of fibers of both flagella appear to lie in the same plane, which coincides with the plane of beat. The two basal bodies lie in a V configuration and are joined at the top by a striated fiber and at the bottom by two smaller fibers. From the area between the basal bodies four bands of microtubules, each containing four tubules, radiate in an X-shaped pattern, diverge, and pass under the cell membrane. Details of the complex arrangement of tubules near the basal bodies are described. It seems probable that the connecting fibers and the microtubules play structural roles and thereby maintain the alignment of the flagellar apparatus. The relation of striated fibers and microtubules to cilia and flagella is reviewed, particularly in phytoflagellates and protozoa. Structures observed in the transitional region between the basal body and flagellar shaft are described and their occurrence is reviewed. Details of structure of the flagellar shaft and flagellar tip are described, and the latter is reviewed in detail.     

荒漠藻壳的精细结构与发育

以宁夏沙坡头不同时期围栏形成的固沙地为样点,将土壤学研究手段与土壤微生物学研究方法相结合,首次在微米层次揭示了荒漠藻壳中藻类植物的自然群落结构和空间分布规律,同时结合矿物物相分析,藻类生物量、土壤理化性质,从生物学、土壤学、矿物学交叉结合的角度深入地揭示了荒漠藻壳的结构和发育,为荒漠拓殖生物群落的发育和人工调控荒漠藻壳固沙培肥技术的应用提供了最直接的依据。另外研究中所采用的多学科交叉结合的实验手段     

离体条件下诱导番茄果实状结构的再生

以番茄（Ｌｙｃｏｐｅｒｓｉｃｏｎ ｅｓｃｕｌｅｎｔｕｍ Ｍｉｌｌ．）雌蕊和幼果的组织作外植体可以诱导果实状结构的再生。这种果实状结构在离体条件下能培养成熟,成熟时具红色。解剖观察表明：果实状结构由果肉和包围在外面的果皮组成,无种子和胎座。外源激素和外植体年龄的试验揭示：１．以雌蕊组织作外植体时,仅附加外源细胞分裂素就可以诱导果实状结构的再生,外源生长素似乎不是必需的,最高的诱导频率（５０．０％ ）出现在仅附加玉米素０．５ ｍ ｇ／Ｌ的组合。２．从直径４—１２ ｍ ｍ 的幼果上分离的外植体在附加外源激素的培养基上均可诱导果实状结构的再生,但只有从直径８ ｍ ｍ 的果实分离的组织块作外植体并将它们培养在６－ＢＡＰ ２ ｍ ｇ／Ｌ,ＮＡＡ０．１ ｍ ｇ／Ｌ的培养基上时,果实状结构的诱导频率最高（６２．５％ ）。为了探讨在果实状结构再生中表现出来的细胞全能性的表达,提出了植物细胞全能性的部分表达（Ｐａｒｔｉａｌｅｘｐｒｅｓｓｉｏｎ ｏｆｐｌａｎｔ ｃｅｌｌｔｏｔｉｐｏｔｅｎｃｙ）的概念并进行了讨论。     

THE FINE STRUCTURE OF MITOSIS AND CELL DIVISION IN THE CHRYSOPHYCEAN ALGA OCHROMONAS DANICA1

At the ultrastructural level, cell division in Ochromonas danica exhibits several unusual features. During interphase, the basal bodies of the 2 flagella replicate and the chloroplast divides by constriction between its 2 lobes. The rhizoplast, which is a fibrous striated root attached to the basal body of the long flagellum, extends under the Golgi body to the surface of the nucleus in interphase cells. During proprophase, the Golgi body replicates, apparently by division, and a daughter rhizoplast, appears. During prophase, the 2 pairs of flagellar basal bodies, each with their accompanying rhizoplast and Golgi body, begin to separate. Three or 4 flagella are already present at this stage. At the same time, there is a proliferation of microtubules outside the nuclear envelope. Gaps then appear in the nuclear envelope, admitting the microtubules into the nucleus, where they form a spindle. A unique feature of mitosis in O. danica is that the 2 rhizoplasts form the poles of the spindle, spindle microtubules inserting directly onto the rhizoplasts. Some of the spindle microtubules extend from pole to pole; others appear to attach to the chromosomes. Kinetochores, however, are not present. The nuclear envelope breaks down, except, in the regions adjacent, to the chloroplasts; chloroplast ER remains intact throughout mitosis. At late anaphase the chromosomes come to lie against part of the chloroplast ER. This segment of the chloroplast ER appears to be incorporated as part of the reforming nuclear envelope, thus reestablishing the characteristic nuclear envelope—chloroplast ER association of the interphase cell.     

FINE STRUCTURE OF MITOSIS AND CLEAVAGE IN FRIEDMANNIA ISRAELENSIS (CHLOROPHYCEAE: CHLOROSARCINACEAE)1

Observations on the ultrastructure of Friedmannia israelensis Chantanachat & Bold revealed the presence of a phycoplast and zoospores with cruciate rootlets. During mitosis, the nuclear envelope partially disintegrates and the basal bodies remain at the cell surface on either side of the developing cleavage furrow. The events during mitosis and cleavage in Friedmannia resemble those reported in the other green algae, Platymonas and Pleurastrum.     

FINE STRUCTURE AND ORGANELLE ASSOCIATIONS IN BROWN ALGAE

The structural interrelationships among several membrane systems in the cells of brown algae have been examined by electron microscopy. In the brown algae the chloroplasts are surrounded by two envelopes, the outer of which in some cases is continuous with the nuclear envelope. The pyrenoid, when present, protrudes from the chloroplast, is also surrounded by the two chloroplast envelopes, and, in addition, is capped by a third dilated envelope or "pyrenoid sac." The regular apposition of the membranes around the pyrenoid contrasts with their looser appearance over the remainder of the chloroplast. The Golgi apparatus is closely associated with the nuclear envelope in all brown algae examined, but in the Fucales this association may extend to portions of the cytoplasmic endoplasmic reticulum as well. Evidence is presented for the derivation of vesicles, characteristic of those found in the formative region of the Golgi apparatus, from portions of the underlying nuclear envelope. The possibility that a structural channeling system for carbohydrate reserves and secretory precursors may be present in brown algae is considered. Other features of the brown algal cell, such as crystal-containing bodies, the variety of darkly staining vacuoles, centrioles, and mitochondria, are examined briefly, and compared with similar structures in other plant cells.     

FINE STRUCTURE OF MEMBRANOUS AND MICROFIBRILLAR SYSTEMS IN THE CORTEX OF PARAMECIUM CAUDATUM

An electron microscope study of the cortex of Paramecium caudatum has revealed new details pertinent to several unresolved problems. The lateral boundaries of the alveoli do not regularly follow the crests of the polygonal ridges and thus their staining with silver cannot account for the external lattice seen by light microscopists. A granulo-fibrillar material is present, however, within the peaks of the ridges, which would account for the external lattice if so stained. Perforations are present between adjacent alveoli which make the whole mosaic of alveolar sacs within the cell's cortex continuous—both the membranes and the lumen. A microfibrillar system exhibiting a cross-striated pattern lies in the superficial cortex. These bands are inserted at their ends in the epiplasm and have a fine structure and arrangement suggesting a muscular function. The infraciliary lattice is a branching system of fibers with electron-opaque posts at the center of each branching locus. This system is distinct from the striated bands in morphology and in space. The epiplasm is discontinuous along the crests of the ridges, which may account for the pellicles' disposition to tear along these lines. A three-dimensional drawing is presented to show the interrelationships between the above membranous and microfibrillar systems.     

蜥臀目霸王龙及有鳞目沧龙牙齿组织的微细结构

本文是利用扫描电子显微镜对陆栖恐龙tvrannosaurid与海栖渐增mosasaurid”牙齿结构进行的比较解剖学研究。化石采自加拿大RedDeerhiverValley上白里统Horse－shoeCanyon组。通过研究地层中出现的生物化石,特别是动物牙齿的组织结构,可以了解动物为了适应生活环境而发生的进化过程,也可以推测它们的系统发育关系。tyrannosaund与mosas。id都拥有锥状的同形齿,牙齿侧向扁平,且略向后弯曲。研究结果确认了tyrannosaurid的牙齿由于薄层的无柱釉质bPrismaticenamel）向齿质的侵人而造成许多的凹凸构造,此锯齿状构造沿着牙齿的前后缘,由牙齿的顶端分布至基部。因此tyrannosaurid的牙齿呈现着锐利的切缘;在这些凹凸状切缘的沟与小窝的深部可观察到有机物的沉积。但是类似的锯齿状构造只能在齿冠呈钝圆状的mosasaurid牙齿的基部附近观察到。我们以扫描电子显微镜（SEM）检索,确认两爬行类的齿质皆是属于中间型的真性齿质（intermediatetypeorthodentine）;所谓orthodentine即是细管齿质（tubulardentine）。tyrannosaurid的真性齿质的齿质小管只在齿质一釉质相接处Uentino—enamaljunction）附近放散出规则性的分歧与末枝。但mosasaurid的真性齿质的齿质J。管,在齿质的中间层与表层中,呈现着由复杂     

麦冬花药绒毡层和乌氏体的细微结构

麦冬(Ophiopogon japonicus)的绒毡层发育为分泌型。在小孢子母细胞时期,绒毡层细胞达到了发育的高峰。此时,绒毡层细胞中细胞器非常丰富,具大量线粒体、高尔基体和质体,尤以肉质网含量最多;原乌氏体出现较早,在小孢子母细胞时期绒毡层细胞中就已出现;四分体时期,大量原乌氏体被排入内切向面的质膜和纤维素壁之间;到了小孢子早期,绒毡层细胞失去细胞壁,原乌氏体分布在质膜的凹陷处,孢粉素物质在其上沉积,发育为乌氏体,乌氏体有单个和复合两种类型;当花粉成熟时,绒毡层细胞完全解体。     

THE FINE STRUCTURE OF CAPILLARIES AND SMALL ARTERIES

Details of capillary endothelia of the mammalian heart are described and compared with capillaries of other organs and tissues. Continuous invagination and pinching off of the plasma membrane to form small vesicles which move across the cytoplasm are suggested as constituting a means of active and selective transmission through capillary walls (12). This might be designated as cytopempsis (transmission by cell). The fine structure of the different layers in the walls of small heart arteries is demonstrated. Endothelial protrusions extend through windows of the elestica interna to make direct contact with smooth muscle plasma membranes. The elastica interna appears to vary greatly in both thickness and density, and probably restricts filtration, diffusion, and osmosis to such an extent that windows and the transport mechanisms described (cytopempsis) are necessary for the functional integrity of the smooth muscle layer. The contractile material consists of very fine, poorly oriented filaments.