THE MORPHOLOGY AND FINE STRUCTURE OF CERATIUM HIRUNDINELLA (DINOPHYCEAE)1

Some aspects of thecal morphology in Ceratium hirundinella are redescribed by means of scanning electron microscopy. The internal anatomy of the cell has been clearly revealed for the first time in serial sections examined by transmission electron microscopy. An unusual sulcus, termed the sulcul aperture, has been found to open into a large ventral chamber which extends toward the center of the cell. The 2 flagella are inserted at one side of the ventral chamber. The ultrastructure of the flagellar canals and root systems arc described in detail. A microtubular strand has been found to run from near the nucleus to near the flagellar bases but not to conned with either. The fine structure of the theca, trichocysts, nucleus, and chloroplasts is basically similar to that of other dinoflagellates. Food vacuoles are reported. These contain material thought to be undergoing digestion. It is suggested that the food particles enter the cell by way of the ventral chamber, which is lined only by membranes, unlike the rest of the cell, which is covered by thick plates. The new findings are discussed in relation to the earlier work on the species and to the fine structure of oilier dinoflagellates.     

MORPHOLOGY,FINE STRUCTURE,AND ONTOGENY OF THE STINGING EMERGENCE OF URTICA DIOICA

Stinging emergences in Urtica dioica L. characteristically possess an elongate stinging cell and a multicellular pedestal. The emergence is derived from the epidermal and subepidermal cell layers. The apical wall of the stinging cell is composed of silica bodies which decrease basipetally in concentration. The basal portion of the cell wall of the stinging cell is devoid of silica bodies and lacks primary pit fields or pits between it and the pedestal cells. X-ray microanalysis of electron dense particles located in the stinging cell ER-golgi complex indicate that these particles contain silicon. There is no ultrastructural evidence for the presence of a toxin synthesizing system or a toxin itself.     

MORPHOLOGY,FINE STRUCTURE AND ONTOGENY OF THE STINGING EMERGENCE OF TRAGIA RAMOSA AND T. SAXICOLA (EUPHORBIACEAE)

The ontogeny and ultrastructure of Tragia ramosa and T. saxicola are described. The stinging emergence of T. ramosa and T. saxicola consists of a central stinging cell and three lateral cells. The stinging cell possesses a compound crystal in the apical region which is held in place by cell wall extensions. The stinging cell cytoplasm is characterized by a large central vacuole which contains a proteinaceous substance as determined histochemically. Upon contact, the stinging cell wall is pushed back over the crystal, exposing it to penetrate an individual. This stinging mechanism is unique among stinging emergences. The stinging cell is subepidermal in origin whereas the three lateral cells are epidermal in origin. The morphology, ultrastructure and ontogeny of the stinging emergence of T. ramosa and T. saxicola appear to be identical.     

A GREEN DINOFLAGELLATE WITH CHLOROPHYLLS a and b: MORPHOLOGY,FINE STRUCTURE OF THE CHLOROPLAST AND CHLOROPHYLL COMPOSITION1

A green-colored marine unicell has been grown in unialgal culture and its morphology, chloroplast fine structure, and chlorophyll composition investigated. The organism is typical of dinoflagellates in its shape, flagellation, nucleus, mitochondria, and trichocysts. It is similar to Gymnodinium but possesses fine body scales. Chloroplasts and two kinds of vesicles bounded by double membranes, but no organelles obviously identifiable as nuclei or mitochondria, are associated in ribosome-dense cytoplasm separated by a double membrane from the dinophycean cytoplasm. The chloroplasts are unlike any previously reported for dinoflagellates. Each is enclosed by an envelope consisting of a double membrane. Chloroplast lamellae consist of three appressed thylakoids. Interlamellar pyrenoids are present. Pigment analysis reveals chlorophylls a and b but not chlorophyll c. It seems likely that the organism is an undescribed dinoflagellate containing an endosymbiont with chlorophylls a and b and that the reduction of the endosymbiont nucleus and mitochondria has permitted a more initmate symbiosis.     

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.     

FINE STRUCTURE AND CYTOCHEMISTRY OF LILIUM POLLEN TUBES

Growth of the Lilium longiflorum pollen tube in vitro is restricted to a zone extending back 3–5 μ from the tip. Electron micrographs of cross and longitudinal thin sections of L. longiflorum and L. regale pollen tubes reveal that the cytoplasm of the nongrowing region of the tube contains an abundance of mitochondria, amyloplasts, Golgi bodies, endoplasmic reticulum, lipid bodies, and vesicles. In contrast, the growing tip is characterized by an abundance of vesicles and an absence of other cytoplasmic elements. The vesicles appear to be of 2 types. One is spherical, about 0.1 μ in diameter, stains strongly with phosphotungstic acid, apparently arises from the Golgi apparatus and appears to contribute to tube wall and plasmalemma formation. The other type is irregular in shape, 0.01-0.05 μ in diameter, stains strongly with lead hydroxide, and is of unknown origin and function. Cytochemical analysis indicates that the tips of L. longiflorum pollen tubes are singularly rich in ribonucleic acid, protein, and carbohydrate. These findings are discussed in relation to tube growth.     

FINE STRUCTURE OF THE DIATOM AMPHIPLEURA PELLUCIDA. II. CYTOPLASMIC FINE STRUCTURE AND FRUSTULE FORMATION

The general arrangement of cytoplasmic organelles in Amphipleura pellucida Kutz. is similar to that in other naviculoid diatoms. The chromatophores are parietal with a single, non-membrane-limited, pyrenoid. The pyrenoid is crossed by several double-disc lamellar bands which are occasionally interrupted by less dense areas containing convoluted tubules. Similar areas also interrupt the three-disc bands of the chromatophores. The nucleus is irregular in shape. The outer membrane of the porous nuclear envelope outfolds around the chromatophore. A perinuclear dictyosome complex is present. Amorphous dense bodies are formed in elaborations of the dictyosomes. Vesicles, both with and without dense inclusions, are formed by the dictyosomes during cell division and a role is suggested for these vesicles in both cytokinesis and frustule development. The first evidence of frustule formation is the deposition of the siliceous median rib within a membranous sac. This sac expands laterally to form the silica deposition vesicle which appears to serve as a mold for the formation of the valve. After the valve is formed, the membranes and the small amount of cytoplasm external to it are sloughed off.     

FINE STRUCTURE OF CHROMOSOMES

Electron micrographs of staminate hair cells of Tradescantia reflexa indicate that early prophase chromosomes are composed of a number of helically arranged chromonemata. Favorable preparations reveal as many as 64 identifiable subsidiary strands, assumedly arranged as intertwined pairs to form a hierarchy of pairs of pairs. The helices of the smallest discernible units have a diameter of about 125 A, with highly electron-scattering material disposed peripherally around a less dense "core." The wall of this peripheral ring has a thickness of about 40 A, and apparently represents another pair of coiled threads surrounding a 40 A central axis. The implications of the findings are discussed briefly.     

FINE STRUCTURE AND REPLICATION OF THE KINETOPLAST OF TRYPANOSOMA LEWISI

The kinetoplastic DNA of Trypanosoma lewisi is described as a filamentous body lying within a mitochondrion, with the filaments oriented parallel to the long axis of the cell. The manner of fixation, the replicative state, and perhaps the physiological state of the cell, may result in slight morphological differences among such bodies. The kinetoplastic DNA replicates to form "left" and "right" rather than "upper" and "lower" members, and both the kinetoplast and nucleus incorporate radiothymidine as shown by radioautography. Radioautographic analyses suggest a random incorporation of radiothymidine by kinetoplasts. Silver grains were occasionally observed over centriolar elements. Finally, the observations are discussed with respect to the sequential replication of the aforementioned organelles by T. lewisi.     

FINE STRUCTURE OF CALONEIS AMPHISBAENA (BACILLARIOPHYCEAE)1

The structure of the motile pennate diatom Caloneis amphisbaena Cleve is described, with emphasis on the lateral, lobed pyrenoid with neither a limiting membrane nor penetration by thylakoids, an interphase nucleus with centers of condensed chromatin, paired dictyosomes, and mitochondria cradled within the chambers of the valve. Microfilaments forming two bundles which lie beneath each raphe slit are of the same size and appearance as actin microfilaments associated with other motile systems.     

棉铃虫蛾复眼的形态及显微结构

棉铃虫[Heliothis armigera(Hubner)]蛾复眼的外形约为椭球体绕长轴等切的2/5。最前和最后小眼之间的夹角约为150°,而最上和最下小眼之间的夹角约为180°,一个复眼大约包括8,900个小眼。每个小眼有一套由角膜、晶锥细胞及晶锥所组成的屈光器和分布在不同水平面上的7-9个小网膜细胞。其周围被6个次虹膜细胞所包围。两个明显可见的区域性差异为:1)复眼不同区域内小眼长度不等,背部区域最短,侧、后、腹和前各区域相继增加。2)背部区域视杆中段的横切面为矩形,其它区域的视杆为放射形。本文将小眼及其周围,从远端到基部分13个层次进行了结构上的描述。     

FINE STRUCTURE OF POTATO STARCH

Sterling, Clarence, and Jack Pangborn. (U. California, Davis.) Fine structure of potato starch. Amer. Jour. Bot. 47(7) : 577–582. Illus. 1960.—Electron micrographs were made from replicas of fracture surfaces of Lintnerized potato starch. These showed that much of the starch substance is organized into radially arranged microfibrils of 220–320 A diameter and considerably greater length (at least over 4000 A). The microfibrils have parallel longitudinal ridges on their surfaces. These ridges are conceived to be outer projections of micellar strands' which are 80–90 A in diameter and occasionally at least up to 4000 A long. The diametral dimension was confirmed by X-ray diffraction study of moist and dry, normal and Lintnerized potato starch. The X-ray evidence also supported the electron micrographic interpretation that amorphous regions lie between the crystalline micelles. On the basis of X-ray data, it was speculated that the molecules in a microfibril are all oriented alike.