Oblique Walls Research Articles

Daylighting of buildings in a hot climate

The utilization of daylight in buildings can save energy and reduce pollution. Furthermore, daylight is preferred by most people because of the spectral composition and the contact with the outside world which is provided by windows. On the other hand, glare and heat gains during the hot season should be avoided. This can be achieved only by careful control of the admitted solar radiation. As a rule, direct sunlight inside the building should be avoided, at least during the hot season. An advanced computer package, based on accurate analytical equations for the calculation of daylight, has been developed for overcast as well as clear sky conditions. The package is meant to be readily usable by non-specialists in computer programming. Complicated configurations of interiors, with any given wall thickness, having rectangular or oblique walls and partitions, can be computed. Furthermore, the same package is extended to deal with the total thermal balance of the building.

A stellar-wind focusing mechanism as an explanation for Herbig-Haro objects

view Abstract Citations (108) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A stellar-wind focusing mecanism as an explanation for Herbig-Haro objects. Canto, J. ; Rodriguez, L. F. Abstract The steady state solution for the interaction of an isotropic stellar wind with a homogeneous, isothermal nebular environment is a spherical cavity, filled by unshocked stellar wind, and bounded by a shock. The radius of the shock is determined by the condition of balance between the ram pressure of the wind and the ambient gas pressure. In this paper, the interaction of an isotropic stellar wind with a nebular environment having a pressure gradient is considered. This situation is expected to apply for recently formed stars located at the edge of a dark cloud. The resulting static configurations are ovoid-shaped cavities with the star located near the tip closer to the high-density region. The stellar wind suffers a first shock against the oblique walls of the configuration and is refracted in the form of an annular stream toward the distant tip of the cavity. At this point a second shock occurs when the stream is forced to move away from the star. Upon cooling, this gas radiates with the characteristic parameters of an HH object. This model is applied to HH 1 and found to account satisfactorily for the observations. Publication: The Astrophysical Journal Pub Date: August 1980 DOI: 10.1086/158186 Bibcode: 1980ApJ...239..982C Keywords: Astrophysics; Celestial Mechanics; Herbig-Haro Objects; Stellar Winds; Focusing; Nebulae; Shock Waves; Space Density; Astrophysics full text sources ADS | data products SIMBAD (3)

Le phlo�me deSelaginella willdenowii: histophysiologie compar�e

Metaphloem sieve elements ofSelaginella willdenowii are elongated cells with slightly oblique or transverse end walls. Pores are seen on both lateral and end walls, although they are more numerous on the latter. Parenchyma cells exhibiting strong enzyme activities (acid phosphatase, non specific esterase, succinate dehydrogenase, cytochrome oxidase, peroxidase) are present between sieve elements and tracheids in each vascular bundle. A functional association thus appears to exist between these parenchyma cells and the conducting elements.—The occurrence of transverse to slightly oblique end walls in sieve elements seems to characterize the ligulate Lycopsids (as opposed to the aligulateLycopodium where sieve elements possess slanting, very oblique, end walls).

Side branch formation and orientation in the caulonema of the moss,Funaria hygrometrica: Normal development and fine structure

The regular branching of theFunaria caulonema filaments is partly related to rhythms in nuclear and cell division. The formation and development of the branches were studied by light and electron microscopy with particular attention directed to the distribution of microtubules and the polar organization of the cytoplasm. The new side branch breaks through the wall of the mother cell. The site of branch development is determined by the position of the nucleus of the mother cell. In protonemata which grow in vertically placed Petri dishes gravity influences the position of nuclei and side branches, and also the direction of oblique cross walls in the caulonema filaments to a certain extent.

A Study of Stelar Ultrastructure in the Heterosporous Water Fern Marsilea quadrifolia L

Sieve tube elements occur in the rhizomes and petioles of Marsilea quadrifolia. These are either thick walled with compound sieve plates in oblique end walls or thin walled with simple sieve plates in transverse end walls. Vessels are restricted to the metaxylem in the roots where the phloem contains sieve cells only. The sieve pores are invariably callose lined and as in other pteridophytes, excepting the Lycopsida, refractive spherules are ubiquitous in the sieve elements of Marsilea. The lumina of the protoxylem tracheary elements in the rhizomes and petioles are occluded by tyloses but probably remain functional in the roots. Pericycle cells backing on to the root protoxylem arms possess wall ingrowths. Transfer cells are however absent from the vascular tissue of the rhizomes and leaves. It is suggested that their presence in the root pericycle is related to the retrieval of ions from the xylem sap which may be particularly critical in water plants. The incidence of transfer cells in cryptogams appears to be far more sporadic than in angiosperms. The root endodermis of Marsilea possesses a casparian strip and abundant vacuolar tannin deposits. Plasmalemmasomes are numerous adjacent to the pericycle transfer cells.

THE PHLOEM OF ETAPTERIS LECLERCQII AND BOTRYOPTERIS TRIDENTATA

The phloem of Etapteris leclercqii and Botryopteris tridentata petioles is described from Lower Pennsylvanian coal balls. Petioles of B. tridentata are characterized in transverse section by an omega‐shaped xylem trace, a phloem zone which extends from 2‐10 cells in width, and 2‐parted cortex. Etapteris leclercqii petioles exhibit a 4–9 cell‐wide phloem zone surrounding the central clepsydroid xylem mass, and a 3‐parted cortex. In both taxa a 1–2 cell layer parenchyma sheath separates the xylem from the extra‐xylary tissues. The phloem of both species consists of sieve elements that average about 20 μm in diam by 200 μm in length in Botryopteris, and 100 μm in length in Etapteris, with horizontal‐slightly oblique end walls. In transmitted light, the radial walls of the sieve elements form an irregular reticulate pattern enclosing elliptical lighter areas. With the scanning electron microscope, these areas appear as horizontal‐slightly oblique furrows on the cell wall, with many small indentations lining the furrows. These indentations, because of their regular occurrence and size (from a few fractions of a micron up to 1.0 μm in diam), are interpreted as sieve pores, and the elliptical areas that enclose them as sieve areas. The phloem of E. leclercqii and B. tridentata is compared with that described for other fossil genera and with that of extant ferns.

The Phloem of Etapteris leclercqii and Botryopteris tridentata

The phloem of Etapteris leclercqii and Botryopteris tridentata petioles is described from Lower Pennsylvanian coal balls. Petioles of B. tridentata are characterized in transverse section by an omega-shaped xylem trace, a phloem zone which extends from 2-10 cells in width, and 2-parted cortex. Etapteris leclercqii petioles exhibit a 4–9 cell-wide phloem zone surrounding the central clepsydroid xylem mass, and a 3-parted cortex. In both taxa a 1–2 cell layer parenchyma sheath separates the xylem from the extra-xylary tissues. The phloem of both species consists of sieve elements that average about 20 μm in diam by 200 μm in length in Botryopteris, and 100 μm in length in Etapteris, with horizontal-slightly oblique end walls. In transmitted light, the radial walls of the sieve elements form an irregular reticulate pattern enclosing elliptical lighter areas. With the scanning electron microscope, these areas appear as horizontal-slightly oblique furrows on the cell wall, with many small indentations lining the furrows. These indentations, because of their regular occurrence and size (from a few fractions of a micron up to 1.0 μm in diam), are interpreted as sieve pores, and the elliptical areas that enclose them as sieve areas. The phloem of E. leclercqii and B. tridentata is compared with that described for other fossil genera and with that of extant ferns.

Observations of oblique magnetic domain walls in nickel single crystals by X-ray topography

Abstract Unusual band images observed by dynamical diffraction X-ray topography in nickel single crystals are elucidated by a model of very thin magnetic domains which extend obliquely through the thickness of the crystal. These thin domains have a magnetization direction which would cause free-pole formation on the crystal surface. In order to avoid these free poles, it is assumed that the magnetization direction of these thin domains rotates away from (111) near the crystal surface. This rotation would cause curvature of the magnetic domain walls near the crystal surface. In this work such curvature is detected in the topographs by differences in the atomic displacement associated with the domain wall near the crystal surfaces and in the interior.

Wood anatomy of theSarraceniaceae; ecological and evolutionary implications

The wood of theSarraceniaceae has a considerable number of primitive features including scalariform perforation plates, long and oblique end walls, scalariform lateral wall pitting, solitary vessels, tracheids with scalariform pitting, and diffuse axial parenchyma. Vessel elements in the genusHeliamphora have the greatest number of primitive features, while vessel elements inDarlingtonia andSarracenia appear to have modifications relating to temperate climates. The wood anatomy suggests thatHeliamphora is growing in a habitat more similar to the original habitat for the family thanDarlingtonia andSarracenia. The wood of theSarraceniaceae is similar to the wood of theTheales.

Primitive-like metaphloem sieve elements in the aerial stem ofEquisetum hyemale

Internodal metaphloem sieve elements located near the nodes of aerial stems ofEquisetum hyemale contain very oblique end walls. During maturation, the connections, or plasmodesmata, in these walls undergo little or no structural modification. By contrast, the endwall connections uniting the protoplasts of mature sieve elements elsewhere in the aerial stem ofE. hyemale are pores.

ULTRASTRUCTURE OF THE NACREOUS LEPTOIDS (SIEVE ELEMENTS) IN THE POLYTRICHACEOUS MOSS ATRICHUM UNDULATUM

The physiological phloem equivalents, leptoids, of the polytrichaceous moss Atrichum undulatum appear to be similar to the nacreous sieve elements that occur in many higher plants. These leptoids are elongated cells with nacreous thickenings on their radial and tangential walls. Their oblique end walls, which lack such thickenings, are traversed by numerous pores through which the plasmalemma, endoplasmic reticulum, and cytoplasm are continuous between adjacent leptoids of a longitudinal file. These end walls closely resemble the simple sieve areas of the sieve elements found in Polypodium vulgare. The leptoid sieve pores have a median expanded area and frequently are occluded by small amorphous protein plugs at each end. Also, callose was observed as electron‐luscent areas both on the faces of the end walls and as a thin cylinder surrounding the lateral area of each pore. Amorphous and granular cytoplasmic contents of the leptoids appear to be morphologically similar to the slime (P‐protein) found in the sieve‐tube elements of many angiosperms. Differentiating leptoids are characterized by the formation of numerous membrane‐bound protein bodies in close association with polysomes and endoplasmic reticulum. As the leptoid matures, the contents of the protein bodies become dispersed in the cytoplasm. Ultrastructurally and ontogenetically the leptoids in the gametophores of A. undulatum appear almost identical to the sieve elements of P. vulgare and therefore should be considered sieve elements rather than phloem‐like equivalents.

A Note on the Gametophytes of Cystopteris tenuisecta

Taxonomically the genus Cystopteris Bernh. was divided into two subgenera, Cystopteris and Acystopteris, by Blasdell (1963). Gametophytes of several members of subg. Cystopteris, such as C. douglasii, C. protrusa, C. diaphana, C. bulbifera, and C. fragilis (Blasdell, 1963; Kaur, 1963; Bir & Trikha, 1970), have been studied, but up until now no observations have been made on the gametophytes of members of subg. Acystopteris, to which the Asiatic species C. tenuisecta (Blume) Mett. belongs. Furthermore, this species has also been referred to Cornopteris by Tardieu-Blot (1958). Therefore, the present study was made to find out the relationship of C. tenuisecta to the other members of the genus and also to see if it really belongs to Cystopteris or not. Cystopteris tenuisecta grows luxuriantly along open roadsides at Tiger Hill (alt. 2,400 m), Darjeeling (Eastern Himalayas). Both tetraploid sexual (n = 84) and triploid hybrid (2n = 126) individuals are abundant (Bir, 1961). The present study concerns only spores collected from tetraploid plants because the spores of the triploid did not germinate even after several trials. Gametophytes were raised by sowing the spores on full strength as well as on half-strength Knop's Solution. These were transferred to sterilized garden soil in pots when they were just expanded. Freshly collected spores take about five or six weeks to germinate. Early stages of germination are very like those described earlier for other leptosporangiate ferns, such as Hypodematium crenatum (Loyal, 1960) and Diplazium (Athyrium) esculentum (Mehra, 1949; Nayar, 1960). On germination the exine ruptures irregularly near the central region of the spore, and a green germ filament emerges, followed by the first rhizoid. Sometimes after exine rupture the rhizoid emerges before the germ filament (Figs. 1, 2). When the germ filament becomes 4-6-celled, an apical cell is cut off by formation of two oblique walls in the terminal 98

Observations on Metaphloem in the Vegetative Parts of Palms

Metaphloem was studied in available vegetative parts of 374 species in 164 genera of palms. Sieve elements usually have compound sieve plates except in the subfamilies Lepidocaryoideae and Nypoideae. Sieve elements in roots usually have oblique to very oblique end walls, whereas in stems and leaves they have transverse to oblique walls. Within a phloem strand the degree of compounding of a sieve plate is directly correlated with element diameter. Plastids are normally present in functioning, enucleate sieve elements. Small quantities of “slime” substances have been detected in young sieve elements in stems and petioles of a few species. Many sieve plates in functioning sieve elements lacked callose in materials quick-killed in liquid nitrogen or chilled acetic-alcohol. Definitive callose is confined to sieve elements just before their obliteration. Sieve tubes in leaf and stem are usually ensheathed by contiguous parenchyma cells while those in root have very few contiguous parenchyma cells. Two types of contiguous parenchyma cells can be distinguished by difference in cytoplasmic density, especially with the electron microscope. Cells with denser cytoplasm are interpreted as companion cells. Lignified contiguous parenchyma cells are occasionally present in metaphloem of petioles. The possible diagnostic and taxonomic features of metaphloem are discussed.

OBSERVATIONS ON METAPHLOEM IN THE VEGETATIVE PARTS OF PALMS

Metaphloem was studied in available vegetative parts of 374 species in 164 genera of palms. Sieve elements usually have compound sieve plates except in the subfamilies Lepidocaryoideae and Nypoideae. Sieve elements in roots usually have oblique to very oblique end walls, whereas in stems and leaves they have transverse to oblique walls. Within a phloem strand the degree of compounding of a sieve plate is directly correlated with element diameter. Plastids are normally present in functioning, enucleate sieve elements. Small quantities of “slime” substances have been detected in young sieve elements in stems and petioles of a few species. Many sieve plates in functioning sieve elements lacked callose in materials quick‐killed in liquid nitrogen or chilled acetic‐alcohol. Definitive callose is confined to sieve elements just before their obliteration. Sieve tubes in leaf and stem are usually ensheathed by contiguous parenchyma cells while those in root have very few contiguous parenchyma cells. Two types of contiguous parenchyma cells can be distinguished by difference in cytoplasmic density, especially with the electron microscope. Cells with denser cytoplasm are interpreted as companion cells. Lignified contiguous parenchyma cells are occasionally present in metaphloem of petioles. The possible diagnostic and taxonomic features of metaphloem are discussed.

Phloem Studies in the Pteridophytes, Part I. Equisetum

Xylary tissues of the pteridophytes have beeii studied in detail by several workers, but phloem tissue has received very little attention. The probable reason for this is the difficulties encountered in studying the anatomical structure of the phloem, for example in cutting perfect radial longitudinal and cross sections of sieve elements showing the details of sieve areas and in staining the tissues. Little is known about the phloem anatomy of Equisetum. I have studied phloem in the rhizomes and aerial shoots of E. hyemale, E. telmateia, E. arvense, and E. giganteum. This paper concerns only the latter two species. The purpose of this investigation was to gather data on Equisetum phloem that could be compared with presumably comparable tissue described in some American calamites (Agashe, 1964). Johnson (1933), in discussing the origin and development of certain tissues in E. scirpoides, mentioned the occurrence of sieve plates with small pores on the lateral walls of the sieve cells. Golub and Wetmore (1948) described the development of phloem in E. arvense. According to them, protophloem sieve cells may be 3 mm long or more. Their longitudinal walls have many, transversely elliptical, faintly staining sieve areas; such areas are also found on the oblique end walls, but they do not seem to form distinct sieve plates. Mletaphloem sieve cells are longer, larger in diameter, and have densely granular cytoplasm and very thick walls; sieve areas are more common on the end wall in metaphloem than in protophloem. There appears to be some confusion in the literature regarding the definitions of sieve cells and sieve tubes. The presently accepted definitions, according to Esau, Cheadle, and Gifford (1953), who quote Cheadle and Whitford, state that a sieve tube consists of sieve elements joined end-to-end to form a vertical tube-like structure in which sieve areas are more highly specialized on the 74

Water-conducting System of Symphyogyna

THE gametophytes of the liverwort genera Hymenophyton, Podomitrium, Pallavicinia and Symphyogyna contain an internal water-conducting system, which is strikingly analogous to the xyleni of simple vascular plants. This system is composed of one or more strands of narrow diameter, elongate, thick walled, densely pitted conducting cells that are devoid of protoplasmic contents at maturity. The presence of this system was first noted by William Jackson Hooker1 in Jungermannia (now Pallavicinia) lyellii. Leitgeb2 pointed out that the cells of the strand were elongate, possessed oblique end walls and that the cell walls were considerably thickened and possessed close-set pores. Tansley and Chick3 reported that the contents of the cells of the conducting strand disintegrate during development and demonstrated that the strand is actually an efficient water-conducting unit within the thalli.

ONTOGENY AND STRUCTURE OF THE SECONDARY PHLOEM IN PYRUS MALUS

Evert, Ray F. (U. Wisconsin, Madison.) Ontogeny and structure of the secondary phloem in Pyrus malus. Amer. Jour. Bot. 50(1): 8–37. Illus. 1963.—The secondary phloem of apple consists of sieve‐tube elements, companion cells, phloem parenchyma cells, fiber‐sclereids, and ray parenchyma cells. The sieve‐tube elements are generally long, slender cells with very oblique end walls and much‐compounded sieve plates. All sieve‐tube elements initially possess nacreous thickenings. Similar wall thickenings were observed in the differentiating fiber‐sclereids and xylem elements. Of the 245 sieve‐tube elements critically examined, 242 were associated with companion cells. All of the companion cells were shorter than their associated sieve‐tube elements. Young companion cells possess slime bodies which later become dispersed. Callose is often found on the sieve‐tube element side of the common wall between sieve‐tube element and companion cell. In several collections, callose was found on both sides of that wall. The parenchyma cells are of 3 types: crystal‐containing cells; tannin‐and/or starch‐containing cells; and those with little or no tannins or starch. Any type parenchyma cell may be on to genetically related to a sieve‐tube element, that is, may be derived from the same phloem initial as the sieve‐tube element. Morphologically, the phloem parenchyma cells intergrade with the companion cells, the tannin‐ and starch‐free parenchyma cells often being difficult to distinguish from companion cells. Most of the tannin‐ and starch‐free parenchyma cells collapse when the contiguous sieve‐tube elements become nonfunctional. The fiber‐sclereids arise from parenchyma cells which overwinter on the margin of the cambial zone and differentiate in nonfunctional phloem.

THE FREQUENCY OF ANTICLINAL DIVISIONS IN FUSIFORM CAMBIAL CELLS OF CHAMAECYPARIS

THE PROBLEM of cell adjustments in the cambium consequent upon increasing girth has excited the interest of anatomists for many decades. It is known that fusiform initials in coniferous cambia divide by oblique anticlinal walls with the two daughter initials overlapping, but the mechanism of elongation has been the subject of controversy. In 1886 Krabbe (Scott, 1888) originated the concept of sliding growth, a theory which received wide acceptance until recent years when some authors have offered modifications and others have rejected it entirely. Sinnott and Bloch (1939) suggested that elongation of fusiform initials was confined to the cell apices, and introduced the term intrusive for this type of elongation. Priestley (1930a, 1930b) proposed quite another method of cell elongation, known as symplastic growth, whereby adj oining cells elongated together without slipping. He argued that ample time existed for gradual mutual adjustments, having calculated from data supplied in an earlier paper by Bailey (1920) that successive anticlinal divisions in the cambium were widely spaced. He suggested that not more than four successive anticlinal divisions were required in 60 years growth of a pine stem. Curiously, no effort was made to determine the actual frequency of anticlinal division, and except for Klinken's (1914) limited observations on a single piece of Taxus stem, no data have been published on the subject. With the object of acquiring some information on the frequency of anticliiial divisions in fusiform initials and the rapidity of the size changes that follow, investigations were initiated in this laboratory on Thuia and Chamaecyparis. Whalley (1950) has reported on Thuja and the present article presents data on Chamaecyparis.

Life-history of Bonnemaisonia hamifera (Trailliella intricata)

J. Feldmann and G. Feldmann1, when cultivating carpospores of Bonnemaisonia asparagoides, succeeded in getting Hymenoclonium serpens as the tetrasporophyte. The validity of these results, however, was challenged by Kylin2, who supposed that the formations held to be tetraspores by the Feldmanns are in reality only end-cells which have started to divide by oblique walls typical of the adult axis. What, according to the Feldmanns, seems to be a tetrasporophyte is only a branched protonema of the gametophyte. Thus, in Kylin‘s opinion, there are only two phases in the life-history, the gametophyte and the carposporophyte (quoted by Drew3).

Comparative Anatomy and Phylogeny of the Casuarinaceae

1. The chief purposes of this investigation have been to contribute toward a better understanding of the evolutionary status of the Casuarinaceae; to present a thorough anatomical description of the family; and to tabulate, at least provisionally, the outstanding characteristics of twenty-nine species. 2. The anatomy of the secondary xylem of the old wood (wood at some distance from the pith) may be summarized as follows: Growth rings are poorly defined or absent; both tracheids and fibertracheids are found in all but one species, in which only tracheids occur; tracheids generally predominate, and the larger, thinner-walled tracheids are vasicentric; the fiber-tracheids often have very thick walls; the fibrous elements are extremely short to moderately long, mostly short to medium-sized; spiral thickenings occur in the fibrous elements of six species. The range of species means for the number of vessels per square millimeter is from moderately few to very numerous; vessel distribution is universally solit...