Gametophytes of some Ceylonese species of Thelypteridaceae

Gametophytes of 12 species of the family Thelypteridaceae were investigated with Cryo-SEM and conventional SEM. Most of the species have rounded front lobes and rounded lobes extending backwards. Metathelypteris flaccida has a cordate game-tophyte. All species have glandular hairs, which are of different length and could be used as diagnostic character in some cases. In addition 7 of the species investigated have acicular hairs. In Thelypteris confluens the glandular hairs on margins and surfaces are born on cells that protrude from the surrounding cells. It is concluded that the combination of characters makes it possible to distinguish species of different genera with the help of gametophyte characters only.     

Scanning electron microscopy of pollen grains of some species of the genusArum (Araceae)

A preliminary report is given on the pollen morphology of eight species of the genusArum examined by scanning electron microscopy. The pollen grains are spheroidal and their sporoderm sculpture possesses spines. The species vary mainly in number, shape and distribution of the spines on the pollen surface and these characters can be used to differentiate them.     

Scanning electron microscopy of Penicillium conidia

The morphology of conidia in 211 species and 12 varieties belonging to the genus Penicillium Link ex Gray have been studied and compared.According to surface ornamentation, conidia have been classified into six groups: A, smooth-walled (7% of the species); B, delicately roughened (13%); C, warty (28%); D, echinate (10%); E, striate with low irregular ridges (36%); and F, striate with scarce high ridges or bars (6%). Whereas the first two groups are closely related in both shape and average size, a gradual reduction was observed in size and in the length/width (l/w) ratio in the remaining groups. Echinate conidia were globose, having the largest average size. Only four species produced conidia not surpassing 2 m in diameter. Maximum length observed was 8 m, and most elongated conidia had a l/w ratio of 3.5. Forty per cent of the species studied had globose conidia.Conidia of the monoverticillate species were generally smaller, more globose and frequently with ridges. In the Asymmetrica, the conidia were generally larger, and showed ridges in comparatively few species. Conidia of the Symmetrica, which were frequently striate with ridges, presented the most elongated forms. The largest average size was found in the conidia of the Polyverticillata which were generally warty. Finally, we have considered the variations in surface ornamentation of conidia during the evolution of the genus Penicillium and drawn attention to their possible relationship with certain habitats and ways of conidial dispersion.     

Scanning electron microscopy of experimental adiaspiromycosis

Adiaspiromycotic granulomas of mice experimentally inoculated with fungusEmmonsia crescens Emmons et Jellison 1960 were examined by scanning electron microscopy. Their morphology, surface structures, and germinating adiaspores isolated from granulomas are described.     

Scanning electron microscopy of vaginal colonization

Changes in the appearance of the vaginal epithelium of rats during the estrous cycle were seen by scanning electron microscopy. Bacterial colonization of this tissue appeared to be influenced by these changes.     

Scanning electron microscopy of barley protoplasts

Summary Scanning electron micrographs of barley protoplasts were compared using various preparatory techniques. Numerous features were observed which turned out to be artifactual characteristics of the processing procedure used in collecting and dehydrating the samples. The most successful technique gave protoplasts which presumably maintained their natural structural integrity, as judged by retention of sphericity and absence of holes in the plasma membrane. The relative numbers of fragmented protoplasts and cellular organelles was also greatly reduced.     

Scanning electron microscopy of scales from different body regions of three lizard species

The Oberhautchen of scales from the dorsal, parietal, and ventral regions of Sceloporus occidentalis (Iguanidae), Gerrhonotus multicarinatus (Anguinidae), and Anniella pulchra (Anniellidae) were examined with a scanning electron microscope. At low magnification, all scales of S. occidentalis exhibit well-defined outlines of cells belonging to the Oberhautchen layer and the previously overlying clear layer. The dorsal and parietal cells of this species exhibit a minutely dentate Oberhautchen that forms tooth-like spinules 0.2 to 0.5 μ long and arranged in irregular rows. Minute pits 0.1 to 0.3 μ in diameter characterize the Oberhautchen of a ventral scale. Cell outlines are not evident on the scales of G. multicarinatus. The Oberhautchen of dorsal and parietal scales of this species is prominently laminated. Laminae are less prominent on scales of the lateral fold, and no intrinsic surface structure is evident on a ventral scale. In contrast, the fossorial anguinomorph Anniella pulchra exhibits Oberhautchen surfaces with practically no intrinsic microornamentation. However, what appear to be outlines of Oberhautchen cells are visible on the dorsal and ventral scales. These observations suggest that modifications of Oberhautchen microornamentation may have evolved to reduce friction with the substrate or other scales. The lack of pronounced microornamentation of the Oberhautchen on some body scales may indicate that a complex interdigitation between clear layer and Oberhautchen cells is not essential to the sloughing process.     

Scanning electron microscope observations of the spores of some species of Polystichum

Five species of Polystichum are studied under the scanning electron microscope and a comparison made with the light microscope studies of the same species published earlier. The SEM studies present a clear picture of the surface topography, supplying additional information.     

Scanning electron microscopy of bone cells in culture

Summary Embryonic and young rat bone cells have been grown in culture and examined in the scanning electron microscope (SEM). Compared with cells fixed in situ and taken directly from the animal, the cultured osteoblastic cells were smoother, flatter and more extensive and showed tighter intercellular contacts. Some matrix is formed in culture and undergoes at least partial mineralization as judged by the accumulation of Ca and P measured by energy dispersive x-ray analysis. Findings concerning the morphology of the collagen arrangement were indecisive. Some superficial cells, free of surrounding matrix, resembled osteocytes in normal in vivo bone. This may indicate that a proportion of the extracellular matrix produced by the cultured cells failed to polymerise into recognizable bone matrix, and that osteocytic morphology is not dependent upon the physical characteristics of the bone matrix.     

Scanning electron microscopy of primary membrane bone

Summary The organization and the development of primary bone were studied in a number of newborn or foetal mammals. Specimens were derived from long bones, calvaria and mandibles. The surface of the mineral component was exposed by treatment with an organic solvent (hot 1,2 ethane diamine or cold sodium hypochlorite solution) and in the case of some internal surfaces (endosteal surfaces of long bone shafts, endocranial aspects of calvaria and the lining of the dental groove or crypts of mandibles) some success was achieved in dissecting the soft tissues from the bone matrix surface. These surface were studied by scanning electron microscopy. Ground sections of similar material were studied by microradiography.Primary membrane bone was found to be most different from adult lamellar bone on rapidly growing (periosteal) surfaces and in the following respects. 1) Mineralization of both the ground substance and collagen occured close to the mineralizing front, so that a higher level was reached rapidly and without a maturation phase. 2) The mineral clusters at the mineralizing front did not reflect the collagen fibre distribution. 3) The collagen fibre bundles at the matrix surface, at least at internal surfaces, were irregular in size and random in orientation.Mineralizing fronts intermediate in character between those of rapidly forming, periosteal primary bone and adult lamellar bone were found on the uncommon internal forming surfaces and in the walls of vascular channels.Most internal surfaces were resorbing. There was a wide range in the size of the resorption lacunae — the many which were only as large as the osteocyte lacunae exposed by the resorption process may have been caused by uninucleated cells.This work has been supported by a grant from the Medical Research Council. The Stereoscan scannning electron microscope was provided by the Science Research Council, and the microradiographic equipment by Mr. R. V. Ely and the Ely-Webster trust. We would like to thank Mr. P. S. Reynolds, Miss A. J. Sutton and Mr. P. F. Farmer for technical and photographic assistance and Mrs. Jeanne Mills for secretarial assistance.     

Scanning electron microscopy of the chick embryo

Internal anatomical features of developing chick embryos can be examined using the scanning electron microscope in embryos that have been sectioned at varying levels. Standard paraffin sectioning techniques are used. After removal of paraffin, embryos are dried by the critical point method and examined. The resulting scanning electron micrographs have proved to be exceptionally useful in teaching anatomy of embryos.