Microscopic anatomy of the cardiac ganglion of Limulus polyphemus

The morphology of the cardiac ganglion of Limulus polyphemus (L) was examined by reconstructions from stained serial sections. This ganglion is composed of two distinct parts: a fiber tract extending the entire length of the heart and a cellular portion underlying the fiber tract. The cellular portion extends continuously from the third pair of ostia to the posterior terminus of the heart. The mean number of ganglion cell bodies is 231. Most of the ganglion cells are located among the glial elements of the cellular portion. The greatest density of cells is found in segments 5 and 6. Six cell types are recognized: (1) large pigmented unipolar cells approximately 120 μ in diameter with distinct connective tissue capsules around them; (2) large pigmented bipolar cells approximately 120 μ in length which are also encapsulated; (3) pigmented multipolar cells approximately 80 μ in diameter which are free of capsules; (4) small pigmented bipolar cells approximately 40 μ in length which are encapsulated but which are found exclusively within the fiber tract; (5) non-pigmented multipolar cells approximately 30 μ in diameter which are found scattered among the connective tissue elements of the cellular portion; and (6) small non-pigmented cells approximately 10 μ in diameter which are found within the unipolar cell capsule and scattered among the connective tissue elements of the ganglion. The variability in cell numbers and the random location of cells points toward non-specific anatomical connectivity between elements of this ganglion.     

HISTOGENESIS OF LEAF VENATION IN TRIFOLIUM WORMSKIOLDII (LEGUMINOSAE)

The histogenesis of the leaf venation in Trifolium wormskioldii was followed, using whole cleared leaflets and transverse and paradermal microtome sections. Mature leaflets are about 8 mm in length. The midvein precambium appears in leaflets 100 μ in length; secondary vein procambium is first seen in 230 μ leaflets; procambium of minor veins first appears in leaflets 400-600 μ in length. Phloem is apparent before xylem, in midvein, secondary veins, and minor veins. Vein endings are initiated and they mature last. No evidence was found to support the theory of “vein breakage.” In the greenhouse 24 days elapsed from leaf initiation to exposure of leaf tips; 6 more days elapsed until full leaf expansion.     

ASEXUAL DEVELOPMENTAL PATTERNS OF THE DIATOM STAURONEIS ANCEPS IN CULTURE123

During several months under controlled growth conditions, cell division in the diatom Stauroneis anceps resulted in a gradual decrease in length as predicted by the Macdonald-Pfitzer hypothesis. Cells of a clone decreased in average length from 35 to 17 μ. The smallest cell observed measured 12 μ. Cells longer than 26 μ typically had capitate ends. As the cells became shorter, there was a gradual decrease in this capitate configuration with the smallest cells being oval in outline. The estimated increment of size reduction due to cell division in the clone was 0.1 μ per division. This value is dependent on the assumption of random division. Populations with cells less than 28 μ in length showed an increase in valve aberrations, but these cells continued to reproduce. A cell 13 μ long and similar to the smallest specimen of the clone was observed from a core sample with fossil specimens of S. anceps.     

Membrane marker movement on sympathetic axons in tissue culture

In cultures of dissociated chick sympathetic ganglia, retrograde (somatopetal) movement of concanavalin A receptors in the axolemma can be observed directly. Such movement was visualized by using concanavalin A coated red blood cells (ConA-RBCs) as membrane markers. Forty-eight percent of all ConA-RBCs which bound to sympathetic nerve fibers moved somatopetally at rates ranging from 11-84 μ/hr with a mean and standard error of 49 ± 6 μ/hr (n = 18). On nongrowing nerve fibers, the ConA- RBCs within 60 μ of the cell body showed retrograde movement, while on elongating neurites only those markers within 30 μ showed such movement. The rate of retrograde ConA-RBC movement appeared to increase with distance from the cell soma. The binding of ConA-RBCs to sympathetic neurites was specific for concanavalin A receptors since pretreatment with either concanavalin A or α-methylglucopyranoside prevented this binding. Untreated polystyrene beads (1.1 μ) which bound nonspecifically to the neurite membrane also showed retrograde movement. These beads moved somatopetally at rates similar to those of the ConA-RBCs but did so regardless of their initial distance from the soma. These data suggest that retrograde movement of surface elements might be a general property of cultured sympathetic nerve fibers.     

Spore Morphology and Taxonomy of Polypodiaceae

The examination of spores belonging to eight species representing five genera of Polypodiaceae reveals that they are typically free, anisopolar and monolete (bilateral). In a majority of cases the spores are yellow and have a short laesura—about half the length of the greater equatorial axis of the spore. Generally, the spores are elliptical in polar view and plano-convex to concavo-convex in profile view but in cross section they vary in shape. The average measurements in equatorial plane range from 44 μ to 71 μ whereas in the polar direction they vary from 27 μ to 47 μ. The exine is thin (about 2.5 μ and nearly smooth (laevigose-scabrous-foveolose) in Microsorium and Phymatodes but in the other investigated genera, it is thicker, possessing different types of projections. P: E varies from 4.6 to 5.5: 8. Oil globules are present in the spores of some species.

Available data on morphology of spores of Polypodiaceae have been tabulated in two tables on a comparative basis and their importance in taxonomy and phylogeny of some genera have been discussed.     

EMBRYO STRUCTURE AND STORAGE RESERVE HISTOCHEMISTRY IN THE PALM WASHINGTONIA FILIFERA

The seed of Washingtonia filifera (Lindl.) Wendl. is hemispherical and has a smooth testa. The embryo is located on the rounded side of the seed near the raphe. The embryo consists of a prominent single cotyledon, an epicotyl, and a small root apex. The shoot apex is oriented at a right angle to the long axis of the embryo and possesses 2 to 3 leaf primordia. The cotyledon functions as a storage organ and is composed of three cell types with similar ultrastructure. These three types—the parenchyma, protoderm, and procambium—can be distinguished on the basis of position, size, and shape. The procambial strands in the cotyledon consist of a ring of bundles grouped into two distinct sympodia and extend from beneath the shoot apical meristem to the tip of the cotyledon where they are situated very close to the surface. The most prominent organelles within all cell types are protein bodies, lipid bodies, and crystalline protein fibers. The protein bodies contain small crystalline inclusions which are presumed to be phytin. Protein bodies in the protoderm were smaller, denser-staining, and contained fewer crystalline inclusions than those in the parenchyma or procambium. On a volume basis, the parenchyma was shown to be 43% protein bodies, 25% lipid bodies, 15% cytoplasm, 7% cell wall, 4% intercellular space, 2% nuclei, and 4% other organelles (mitochondria and plastids).     

LEAF HISTOGENESIS IN LACTUCA SATIVA WITH EMPHASIS UPON LATICIFER ONTOGENY

The leaf primordia of Lactuca sativa ‘Meikoningen’ develop from a subapical initial in the second layer of the tunica on the side of a fiat shoot apex. Subsequent growth of the subsurface lamina is initiated by submarginal initials which divide anticlinally to produce an adaxial layer and ***a biseriate abaxiallayer, and periclinally to produce a middle layer from which procambium differentiates. The protoderm is derived from the first tunica layer by continuous anticlinal divisions. The activity of the subapical and submarginal initials is completed when the leaf is 0.3 mm in length and 4.0 mm in width, respectively. Continued growth of the leaf to 130-150 mm results from intercalary cell division and enlargement. The mature venation is visibly delineated when the leaf is 25-30 mm in length. Laticifer and phloem cells are initiated by the same mother cells in the ***procambium. The former become non-septate laticifers by resorption of cross walls. They mature concurrently with the phloem and before the xylem.     

STEM ANATOMY AND ASPECTS OF DEVELOPMENT IN TOMATO

Aspects of anatomical development were correlated with internodal growth in tomato plants, variety ‘Yellow Plum,’ grown for more than 3 months. Internodal length was measured weekly in control plants and those harvested for anatomical study. Gross structure indicated progressive development with increasing age. Primary xylem and phloem first mature in distinct strands and the strands are joined laterally by procambium to form a continuous vascular cylinder. Primary phloem occurs on the outer periphery of the procambium between the early-formed vascular strands. Successive periclinal divisions in the procambium during internode elongation give rise to pronounced radial seriations of the cells. Procambial derivatives are included in the cylinder of thick-walled, lignified vascular cells that become prominent after elongation ceases. Secondary xylem is of greater radial width in the stem sectors which include protoxylem. During early secondary growth, vessels develop in the secondary xylem only in these sectors. Nucleate fibers and rays constitute the remainder of the secondary xylem. The rays exhibit an organization noted in other plants of reduced growth habit. Some of these interpretations do not agree with those described for tomato in earlier studies, and they are discussed in relation to pertinent aspects of development.     

Neuronal pathways from the dorsal acelli of the house cricket,Acheta domesticus

Each ocellar nerve in the house cricket Acheta domesticus contains giant nerve fibers of 10-15 μ diameter, characterized in Golgi Cox preparations by a single row of short collaterals which runs along nearly the entire length of a fiber. Numerous long collaterals are given off by thin fibers in the ocellar nerve; medium-size fibers give off relatively few collaterals. The lateral ocellar tracts extend posteriorly through the dorsal protocerebrum, crossing the protocerebral bridge dorsally. The smaller median ocellar tract runs more ventrally through the pars intercerebralis; posterior to the bridge its fibers turn out toward the lateral nerves. Golgi and cobalt preparations reveal branching of giant and mediu_-size ocellar fibers posterior to the bridge at two levels, forming bilateral regions of ocellar neuropile. No ocellar processes appear to be given off to the corpora pedunculata, centra! body, nervi corporis cardiaci, antenna! lobes, or circumesophageal connectives; it is uncertain whether ocellar collaterals extend into the protocerebral bridge or optic lobes. Cell bodies of giant and medium-sized fibers are located in the pars intercerebralis.     

Lankesteria barretti n. sp. (Eugregarinida,Diplocystidae), a Parasite of the Mosquito Aedes triseriatus (Say) and a Review of the Genus Lankesteria Mingazzini*

SYNOPSIS. Lankesteria barretti n. sp. (Eugregarinida, Diplocystidae) is named from the mosquito Aedes triseriatus in Texas. The young cephalins occur within the midgut epithelial cells. When they reach a length of about 150–200 μ they rupture the host cell and are released into the space between the epithelium and the peritrophic membrane, becoming gamonts. These grow to about 140–310 by 40 μ at the anterior end and 12 μ at the posterior end. When the host pupates they enter the lumen of the Malpighian tubules; pairs join in syzygy by their anterior ends and later more laterally. Each pair forms a spherical gametocyst about 60–100 μ (exceptionally 250 μ) in diameter. A large number of oocysts develop in each gametocyst. The mature oocysts are spindle-shaped, 11 by 5.4–5.7 μ, and contain 8 elongate sporozoites and a refractile residuum. The gametocyst wall breaks down, releasing oocysts in the Malpighian tubules of the host when it is adult. The oocysts pass out in the feces and presumably infect new larvae by ingestion. The cephalins and gamonts of L. barretti differ from those of L. culicis (of Aedes aegypti) in having a relatively anterior instead of a central nucleus and in lacking a noticeable mucron; its longitudinal folds are not as well-developed as in L. culicis, and its paraglycogen granules are larger. The fine structure of L. culicis and L. barretti is described in detail. Their gamonts have a polar ring but no definite conoid. The taxonomy of the genus is reviewed, but its species have been so poorly described that it is impossible to be sure whether they are all really Lankesteria. About 19 species have been described (5 from turbellaria, 8 from tunicates, perhaps 1 from Amphioxus, 1 from the chaetognath Sagitta sp., 1 from Phlebotomus and 3 from mosquitoes).     

Ortholinea alata n. sp. (Myxosporea: Ortholineidae) in the Northern Butterfly Fish Chaetodon rainfordi

Ortholinea alata n. sp. is described from the northern butterfly fish, Chaetodon rainfordi collected at Heron Island, Great Barrier Reef, Australia. Spherical, disporous trophozoites (10–15 μ) and spores were observed in the lumina of kidney tubules and collecting ducts. Spores are broadly triangular with two short, broad processes that extend dorsoventrad from the posterior end of each of the two spore valves. Valves are bisected by a suture in the plane of the polar capsules. Spores are 12.6 μ (length) × 9.6 μ (width) × 9.9 μ (length), and at the anterior end contain two spherical, divergent polar capsules measuring 4.6 ( 4.1 –5.1) μ. Sporogenesis is similar to that of renal Sphaerospora spp.: the intraluminal trophozoites of O. alata n. sp. correspond to pseudoplasmodia described for Sphaerospora spp. and no large, multinucleate plasmodia are formed. No significant histopathological changes were observed in the kidneys of infected fish.     

The Oocysts of Eimeria vermiformis sp. n. and E. papillata sp. n. (Protozoa: Eimeriidae) from the Mouse Mus musclus

SYNOPSIS. Eimeria vermiformis sp. n. and E. papillata sp. n. are described from the mouse Mus musculus. The sporulated oocysts of E. vermiformis are 18–26 by 15–21 μ (mean 23.1 by 18.4 μ); its sporocysts are 11–14 by 6–10 μ (mean 12.8 by 7.9 p). The sporulated oocysts of E. papillata are 18–26 by 16–24 μ (mean 22.4 by 19.2 μ); its sporocysts are 10–13 by 6–9 μ (mean 11.2 by 8.0 μ). A substiedal body is present in E. papillata sporocysts. Patent infections were produced in white laboratory mice with both species. Fourteen species of Eimeria have now been described from the genus Mus.     

A trnL-F based phylogeny for species ofPelargonium (Geraniaceae) with small chromosomes

Phylogenetic analysis was performed of 921 positions of trnL (UAA) 5 exon — trnF (GAA) exon chloroplast DNA regions from 68 representatives ofPelargonium sectt.Campylia, Cortusina, Glaucophyllum, Hoarea, Isopetalum, Ligularia, Otidia, Pelargonium, Peristera, Polyactium, andReniformia, together with five putative outgroup species from sectionsCiconium, Chorisma andJenkinsonia. The total data set therefore comprised 67.2 kb of DNA sequence. Two main ingroup clades were identified: one clade contains sectionsPeristera, Reniformia, andIsopetalum, the other contains sectionsCampylia, Cortusina, Glaucophyllum, Hoarea, Ligularia, Otidia, Pelargonium, Polyactium and two species currently grouped in sect.Peristera. Branching order among five main clades within the latter clade was not resolved. The trnL-F sequence data support monophyly only for sectionsReniformia andHoarea, the remainder of the currently recognized sections ofPelargonium being either paraphyletic or polyphyletic. The data further suggest that sect.Polyactium is diphyletic and that sect.Glaucophyllum is nested within sect.Pelargonium. One relatively derived clade, which represents half of the genus, contains predominantly geophytic and succulent species, occurring in the geographically restricted winter rainfall region of the South African Cape. This pattern is interpreted as reflecting explosive radiation, possibly as an adaptive response to recent aridification in the western Cape.     

Asexual genetic variability inAgavaceae determined with inverse sequence-tagged repeats and amplification fragment length polymorphism analysis

Agaves are succulent monocot plants rich in fibers, sugars and other important compounds. They are also valued as ornamental plants and for their ability to grow in poor soils. In the present study, inverse sequence-tagged repeats (ISTR) and amplified fragment length polymorphism (AFLP) analysis were used to study genetic diversity in differentAgavaceae plant samples. Comparison of the banding patterns between the mother plant and rhizome-derived daughter plants showed that genetic variability is generated during asexual reproduction in these species. Phylogenetic relationships amongAgave species were obtained using unweighted pair-group method, arithmetic average (UPGMA) analysis. Genetic diversity through asexual propagation allows for genetic selection and improvement within these asexually propagated plants.     

SHOOT APEX ORGANIZATION AND ORIGIN OF THE RHIZOME-BORNE ROOTS AND THEIR ASSOCIATED GAPS IN DENNSTAEDTIA CICUTARIA

The shoot apex of Dennstaedtia cicutaria consists of three zones—a zone of surface initials, a zone of subsurface initials, and a cup-shaped zone that is subdivided into a peripheral region and central region. A diffuse primary thickening meristem, which is continuous with the peripheral region of the cup-shaped zone, gives rise to a broad cortex. The roots occurring on the rhizomes are initiated very near the shoot apex in the outer derivatives of the primary thickening meristem. The roots that occur on the leaf bases also differentiate from cortical cells. Eventually, those cortical cells situated between the newly formed root apical cell and the rhizome procambium (or leaf trace) differentiate into the procambium of the root trace, thus establishing procambial continuity with that of the rhizome or leaf trace. Parenchymatous root gaps are formed in the rhizome stele and leaf traces when a few of their procambial cells located directly above the juncture of the root trace procambium differentiate into parenchyma. As the rhizome procambium or leaf trace continues to elongate, the parenchyma cells of the gap randomly divide and enlarge, thus extending the gap.     

Electrical activity and structural correlates of giant nerve fibers in Kuruma shrimp (Penaeus japonicus)

Morphology and recordings of electrical activity of Kuruma shrimp (Penaeus japonicus) giant medullated nerve fibers were carried out. A pair of giant fibers with external diameter of about 120 μ and 10 μ in myelin thickness were found in the ventral nerve cord. The diameter of the axon is about 10 μ. Thus there is a wide gap between the axon and the external myelin sheath. Each axon is doubly coated directly by Schwann cells and indirectly by the myelin sheath layer which is produced by those Schwann cells. Impulse conduction velocities of these giant fibers showed a range between 90–210 m/sec at about 22°C. Large action potentials (up to 113 mV, rise time of 0.16–0.3 msec, maximum rate of rise of 650–1250 V/sec, half decay time of 0.2–0.3 msec, maximum rate of fall of 250–450 V/sec and total duration of less than 1.5 msec) could be obtained by inserting microelectrodes or by longitudinal insertion of 25 μ diameter capillary electrodes into the gap but no DC-potential difference was observed across the myelin sheath. Transmyelin electrical parameters were very favorable for fast impulse conduction: myelin resistance of 3 × 10⁴ Ω cm²; time constant of 0.38 msec; myelin capacitance of 1.35 × 10^?8 F/cm²; gap fluid resistivity of 23 Ω cm. The existence of nodes of Ranvier could not be demonstrated morphologically, but electrophysiological evidence suggests that a type of saltatory conduction occurs in these giant fibers.     

Genetic transformation ofPelargonium X hortorum

Summary TransgenicPelargonium X hortorum have been producedvia Agrobacterium tumefaciens-mediated transformation. The regeneration protocol used provided a regeneration frequency approximately to 95 percent. Clumps of regenerants, from cotyledons and hypocotyls ofPelargonium X hortorum seedlings, were inoculated with the disarmed strain EHA101 ofAgrobacterium tumefaciens. This strain contains a binary vector carrying neomycin phosphotransferase II, hygromycin B phosphotransferase and ß-glucuronidase genes. Selection on the regeneration medium supplemented with hygromycin allowed production of transgenic plants in up to 20% of the inoculated explants. The insertion of foreign DNA was demonstrated by Southern and polymerase chain reaction analysis: these experiments indicated that the inserted T-DNA is not full length for most of the plants. All RO transgenic plants exhibited a normal phenotype and are fertile.Abbreviations GUS ß-glucuronidase coding sequence - PCR polymerase chain reaction - CaMV cauliflower mosaic virus - NPTII neomycin phosphotransferase coding sequence - NOS nopaline synthase gene promoter and terminator - HPH hygromycin B phosphotransferase coding sequence - SDS sodium dodecyl sulphate - EDTA (ethylenedinitro trilo)tetra-acetic acid disodium salt     

Sarcomeric domain organization within single skinned rabbit psoas fibers and its effects on laser light diffraction patterns.

Total intensity and fine structure of first-order laser light diffraction maxima from single skinned rabbit psoas fibers were studied. Total intensity of the diffraction maxima was measured as a function of the incidence angle (omega-scan). In the most homogeneous fibers, most of the intensity in the diffraction maxima is confined to a rather narrow range of incidence angles. Fibers with less homogeneous striation patterns, apparently composed of several regions of distinct sarcomere length and tilt of striation (domains), give rise to several narrow intensity peaks in their omega-scans. Left and right first-order diffraction lines produce omega-scans of almost identical shape, composed of one or more intensity peaks, with each pair of corresponding peaks separated by about the same angle. The data indicated that in single skinned rabbit psoas fibers, light diffraction is dominated by Bragg diffraction and that the peaks within omega-scans can be directly correlated with domains within the illuminated fiber segment. In the most homogeneous fiber segments the diameter of domains, estimated from the width of the corresponding maxima in the omega-scans, could almost be as large as the fiber diameter. On average, from the number of peaks in the omega-scans two to three domains with an average length of approximately 250-350 microns can be identified in a fiber cross-section. Therefore, on average only a small number of domains (8 per mm) are found within skinned rabbit psoas fiber segments. In contrast, the number of substructural lines within the diffraction maxima is large even for microscopically homogeneous fibers. Substructural lines appear to be present only when several domains are illuminated simultaneously. Separation and width of these substructural lines are approximately inversely proportional to the length of the illuminated region of the fiber. These data suggest that the substructural lines are due to interference between domains, illuminated simultaneously by a light source with a high degree of spatial coherence (laser). The relevance of these findings for measurements of sarcomere length by laser light diffraction is discussed.     

The fine structure of the limulus optic nerve

Two complete composite photographs of the optic nerve of Limulus, made by electron microscopy, reveal the presence of neurosecretory granules in the large axons of the rudimentary eye neurons. The number of intermediate sized, (3–7 μ), of eccentric cells corresponds with the number of ommatidia as expected, but only their sheath of Schwann cells show an intimate interfolding. Based on the number of fine axons within the nerve each ommatidium has an average of 12–13 retinular cells. The diameter of their fibers is between 0.2 and 3 μ although the majority are between 1 and 1.5 μ. They are aggregated into bundles of six to seven fibers by the sheath cells although some bundles contain only two, others as many as 181 fibers. There is no indication in these studies that retinular cell axons within a bundle are associated with the same, adjacent, or other pattern of ommatidia. The photographs suggest that physiological activity in retinular cell axons might be detected most easily in the smallest bundles because they contain the fewest, but the larger retinular cell axons.