Filament (botany)

“ For microscopical examination the larger species are preferable. When one of these is magnified (Fig. 18, A, C) , the unbranched filament is shown to be made up of perfectly cylindrical cells, with rather delicate walls. The protoplasm is confined to a thin layer lining the walls, except for numerous fine filaments that radiate from the centrally placed nucleus (n) , which thus appears suspended in the middle of the cell. The nucleus is large and distinct in the larger species, and has a noticeably large and conspicuous nucleolus. ”

“ Plants growing in pots were protected wholly from the light, or had light admitted from above or on one side as the case might require, and were covered above by a large horizontal sheet of glass, and with another vertical sheet on one side. A glass filament, not thicker than a horsehair, and from a quarter to three-quarters of an inch in length, was affixed to the part to be observed by means of shellac dissolved in alcohol. ”

“ The whole plant consists of a very long, much-branched, but undivided tubular filament. Where it is in contact with the substratum, root-like outgrowths are formed, not unlike those observed in Vaucheria. At first the walls are colorless, but later become dark smoky brown in color. A layer of colorless granular protoplasm lines the wall, becoming more abundant toward the growing tips of the branches. The spore cases, “sporangia,” arise at the ends of upright branches (Fig. 32, C) , which at first are cylindrical (a) , but later enlarge at the end (b) , and become cut off by a convex wall (c) . ”

“ Occasionally there may be found indications of the characteristic clamp-connections in the septate filaments; a small semicircular branch, which is given off from a mycelium immediately above a transverse wall, bends round to fuse with the filament just below the septum, thus serving as a small loop-line connecting the cell-cavity above and below a cross wall. ”

“ To study the earlier stages of germination it is best to choose specimens in which the masses of spores have not been moistened. By thoroughly wetting these, and keeping moist, the process of germination may be readily followed. Many usually begin to grow within twenty-four hours or less. Each cell of the spore sends out a tube (Fig. 47, C) , through an opening in the outer wall, and this tube rapidly elongates, the spore contents passing into it, until a short filament (basidium) is formed, which then divides into several short cells. ”

“ If the spores are kept in water for a few days they will germinate, bursting the outer brown coat, and the contents protruding through the opening surrounded by the colorless inner spore membrane. The protuberance grows rapidly in length and soon becomes separated from the body of the spore by a wall, and lengthening, more and more, gives rise to a green filament like those we found attached to the base of the full-grown plant, and like those giving rise to buds that develop into leafy plants. ”

“ Sepals, petals, and stamens often pass gradually over the one into the other, the petals becoming narrower by degrees, and bearing anthers on each side of the apex, which gradually become larger anthers in proportion to the filament, until the perfect stamen is developed. The long-stalked leaves are floating, and most frequently cordate, elliptical, leathery, with a shiny surface, sometimes (as in Victoria regia and Euryale ferox) with strongly [387] projecting thorny ribs on the lower surface. In the intercellular passages of the leaves are some peculiar, stellate cells. ”

“ They are colorless, or light yellowish, regularly disposed; but their function is not known. Besides these, certain cells become thick-walled, and form resting cells (spores) for the propagation of the plant (Fig. 7, C. sp.) . In species where the sheath of the filament is well marked (Fig. 7, H) , groups of cells slip out of the sheath, and develop a new one, thus giving rise to a new plant.
The bacteria (Schizomycetes) , although among the commonest of organisms, owing to their excessive minuteness, are difficult to study, especially for the beginner. ”

“ Fig. 299. Stamen of Globe Amaranth; very short filament bearing a single anther-cell; it is open from top to bottom, showing the pollen within.
Fig. 300-305. Stamens of several plants of the Labiate or Mint Family. Fig. 300. Of a Monarda: the two anther-cells with bases divergent so that they are transverse to the filament, and their contiguous tips confluent, so as to form one cell opening by a continuous line. Fig. 301. Of a Calamintha: the broad connective separating the two cells. Fig. 302. Of a Sage (Salvia Texana) ”

“ Fig. 4 is a single elater much magnified, showing it to be a spirally coiled filament, that, by sudden expansion, shoots out the spores just as a child’s toy-gun discharges the arrow. Fig. 5 is a part of the leaf of the Sphagnum moss, common in fresh water, showing the curious spiral arrangement of secondary fibre which is found in the cells, as well as the circular pores which are found in each cell at a certain stage of growth. Just below, and to the left hand, is a single cell greatly magnified, in order to show these peculiarities more strongly. ”

“ It is true that the tops of all well-grown trees are rounded, on a large scale, as equally; but that is because they grow from a central stem, while these mossy mounds are made out of independent filaments, each growing to exactly his proper height in the sphere—short ones outside, long in the middle. Stop, though; is that so? I am not even sure of that; perhaps they are built over a little dome of decayed moss below. [12] I must find out how every [24] filament grows, separately—from root to cap, through the spirally set leaves. ”

“ Each leaf is traversed by two fibro-vascular bundles of entirely different structure from those of the ferns. Each is divided into two nearly equal parts, the wood (x) lying toward the inner, flat side of the leaf, the bast (T) toward the outer, convex side. This type of bundle, called “collateral,” is the common form found in the stems and leaves of seed plants. The cells of the wood or xylem are rather larger than those of the bast or phloem, and have thicker walls than any of the phloem cells, except the outermost ones which are thick-walled fibres like those under the epidermis. ”

“ The male element, on the other hand, is relatively small. It may be conveyed to the female element by an out growth of the wall of its cell, which is short in many Algce and Fungi, but becomes an immensely elongated tubular filament, in the case of the pollen cell of flowering plants. But, more commonly, the protoplasm of the male cells becomes converted into rods or filaments, which usu ally are in active vibratile movement, and sometimes are pro pelled by numerous cilia. ”

“ Where the leaf is one cell thick, the cells are oblong in form, becoming narrower as they approach the midrib and the margin. They contain numerous chloroplasts imbedded in the layer of protoplasm that lines the wall. The nucleus (Fig. 63, C, n) may usually be seen without difficulty, especially if the leaf is treated with iodine. This plant is one of the best for studying the division of the chloroplasts, which may usually be found in all stages of division (Fig. 63, D) . ”

“ A phenomenon similar to one we have already seen in cell-division among plants now shows itself. The nucleus becomes broken up into a number of filaments, which lie together in a bundle, each filament stretching from pole to pole of the spindle. Exactly in its central point every filament shows a knot-like enlargement, and from the close approximation of the knots there results a thick zone of protoplasm in the equator of the spindle. ”

“ Stamens with their short and broad filaments continued beyond the anther-cells, and often coherent with each other. Style usually club-shaped, with the simple stigma turned to one side. Valves of the capsule bearing the several-seeded placentæ on their middle; after opening, each valve as it dries folds together lengthwise firmly, projecting the seeds. Seeds anatropous, rather large, with a hard seed-coat, and a large and straight embryo nearly as long as the albumen; cotyledons flat.—Leaves alternate, with stipules. ”

“ The cells contain so much starch as to make them almost opaque, and potash should be used to clear them. The fibro-vascular bundle is of the radial type, there being two masses of xylem (xy.) joined in the middle, and separating the two phloem masses (ph.) , some of whose cells are rather thicker walled than the others. The bundle sheath is not so plain here as in the fern. The ground tissue is composed of comparatively large cells with thickish, soft walls, that contain much starch. The epidermis usually dies while the root is still young. ”

“ The filaments arising from the carpogonia grow into long thin tubes, which fuse with special cells rich in protoplasm contents; and from these points issue isolated tufts of sporogenous filaments, several of which may form the product of one fertilized female cell. In Naccaria, one of the Gelidiaceae, it is observable that the ooblastema filament, as the tube arising from the fertilized carpogonium has been called, fuses completely with a cell contiguous to the carpogonium before giving rise to the foraging filaments already referred to. ”

“ If this be a correct view of the structure of Euphorbia, it may be expected that the true filament, or upper joint of what has commonly been called filament, should, as in other plants, be produced subsequent to the distinct formation of the anthera, which consequently will be found at first sessile on the lower joint or peduncule, after that has attained nearly its full length; and accordingly this proves to be the case in such species as I have examined. ”

“ The spore fruit now enlarges rapidly, and the outer cells become first yellow and then dark brown, the walls becoming thicker and harder as they change color. Sometimes special filaments or appendages grow out from their outer surfaces, and these are also dark-colored. Shortly before the fruit is ripe, the upper cell of the archicarp, which has increased many times in size, shows a division of its contents into eight parts, each of which develops a wall and becomes an oval spore. ”

“ The fibres of the flax stem are so strong and fine they are woven into linen cloth. The stem of a fern leaf has so many of these tough fibres packed together that it is like wire. Fibres are strings of cells. Each little cell has a thin wall around it like the yeast cell, through which water can easily soak, and air pass. The plant used these strings of cells at first to soak up food and air, then to cling to rocks, then to make leaves and stems and roots and spores and seeds. Finally she bound them in bundles to help her stand alone.
The fern is nature's first effort to make bones in plants. ”

“ By making a series of longitudinal sections with a sharp razor through the top of the plant, and magnifying sufficiently, it is found to end in a single, nearly hemispherical cell (Fig. 23, B, S) . This from its position is called the “apical cell,” and from it are derived all the tissues of the plant. Segments are cut off from its base, and these divide again into two by a wall parallel to the first. Of the two cells thus formed one undergoes no further division and forms the central cell of an internode (y) ; the other divides repeatedly, forming a node or joint (x) . ”

“ They form large, dark green, felted masses, and are sometimes known as “green felts.” Some species grow also on the wet ground about springs. An examination of one of the masses shows it to be made up of closely matted, hair-like threads, each of which is an individual plant.
In transferring the plants to the slide for microscopic examination, they must be handled very carefully, as they are very easily injured. Each thread is a long tube, branching sometimes, but not divided into cells as in Spirogyra or Cladophora. ”

“ If a little of the fermenting liquid is examined microscopically, it will be found to contain great numbers of very small, oval cells, with thin cell walls and colorless contents. A careful examination with a strong lens (magnifying from 500–1000 diameters) shows that the protoplasm, in which are granules of varying size, does not fill the cell completely, but that there are one or more large vacuoles or spaces filled with colorless cell sap. No nucleus is visible in the living cell, but it has been shown that a nucleus is present.
If growth is active, many of the cells will be seen dividing. ”

“ The form of the filament has been governed by the need to hold within a bulb of given size a carbon of a given length. The filament must have a uniform section, and that is most certainly obtained in those which are formed by squirting a viscous solution of cellulose into a precipitating solution. The filament material is wound upon blocks of carbon and baked under great heat. Uniformity in resistance, securing equal consumption of current, of surface, and of incandescence, is also indispensable. ”

“ In order to bring out the structure of the protoplast (living part of the cell) , it will be necessary to begin with the living part of the plant and to use the long paraffin method or the collodion method.
Small fragments of a leaf, stem, or root-tip are placed in chromic-acid solution, acetic alcohol, picric acid, chromacetic acid, alcohol, etc., depending upon the nature of the specimen under observation. ”