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As there are many cells pressing each other, the cells are compressed and will appear in such a section quadrangular. The protoplasm flows around the interior the cell in a steady current, carrying with the green chlorophyll bodies and the large transparent colorless nucleus, which however, readily seen because its refractive power differs from that the protoplasm nod the cell-fluids the cellWalls are also plainly seen. In ordinary language often speak the vegetable cell when really mean the empty cell-wall, as Id the microscopical preparations from which have removed the cell-contents cheapest essays writing services as already explained, but should not forget that this use the word cell In describing the structure a drag Is conventional and not scientifically correct. The cell-wall Is formed from and the protoplasm, and once formed not re-absorbed. It alive only in the sense In which hair or fingernails are alive It called formed material, and once formed remains even after all life has ceased In the cell and the protoplasm has all been absorbed from the cell. The size vegetable cells Is extremely variable, for while the average cell Is stated Carpenter about, As already stated, the typical shape a single cell round, but It may also occasionally oral a and in the figure. When cells are joined together, mutual pressure at the points contact apt modify the shape, as in the long thread-like dissertations online filaments many algae, when the cells become cylindrical, as and this shape also fonnd in the soft interiors many plants in which the aggregations cells not a mere thread, as in the soft parts sarsaparilla.

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If only a few cells are joined form a vegetable hair, the Individual cell may assume the conical shape shown in But in the interior parts plants more common that the cells are compressed from all directions, and the shape becomes more or less regularly twelve-sided, as, which in section will appear as six-sided and if the growth more rapid.

in one direction than in others the cells will elongated in that direction as in and but they will still appear six-sided section.

Occasionally the cells may more or less prismatic in shape, as in or, but this not common. All such cells abutting each other with broad surfaces are parenchymatous cells they are uflually not much longer than they are broad, and are usually soft-walled, and therefore they not give much strength the plant.

An important modification the shape cells that figured at where the cell shown as elongated and pointed at the ends, the fusiform or spindle-shaped cell in the tissues the plant the ends these cells interlace high school essay help and as they are usually hardened, or lignified woody, they give strength plants. The wood our trees, for example, made such fusiform cells which often are ten or even a hundred times as long as they are broad, and these cells are called prosenchymatons cells.

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When the cell young completely filled with protoplasm, essays on the help a portion which may differentiated from the remainder as form the nucleus. The cell-wall may scarcely more than a delicate layer the outside the cell in its earlier stages, but this soon becomes surrounded with a denser wall cellulose.

When a cell this kind subjected the action any medium capable attracting water from the protoplasm the latter will sbriuk away from the cell-wall and will then appear surrounded a delicate membrane which called the primordial utricle but this membrane possibly only a product the chemical action the medium the protoplasm, and probably no more a membrane than seen when carefully open an egg iuto boiling water, when the white egg the outside at once coagulates nnd appears a white essay on service membrane around the still transparent albumen within.

This contraction the protoplasm the action reagents, such as glycerin, alcohol, etc. seen in the accompanying figure, which the stellate crystals oxalate lime which are plentiful As the cell grows older and larger, spaces occur in the protoplasm which are fllhd with a ery fluid such spaces are called vacuoles, aud the fluid which they contain called the cell-sap, which increases in volume until the protoplasm occupies but a small part the cell contiguous the cell-wall and finally disappears altogether. The cell then ceases take active part in the life the plant and serves mechani cally osmosis through its cell-walls, or capillary attraction, carry moMure from the rootlets the growing and living cells the plant. At last this too may cease and the dry cell, empty or filled with mineral legit essay writing services or other deposits, as in the inner or hear, wood trees, serves only as mechanical support the living tissues. From the protoplasm may elaborated various organic substances which are importance in the economy the plant and the moisture taken from the soil holds in solution more or less inorganic material which carried into the tissues the plant, where finally deposited without, however, necessarily taking part in the life processes the plant. As evaporation moisture from the plant takes place mainly from the leaves here that much this inorganic material deposited, and upon burning different parts plants and weighing the residue fouud that leaves leave the largest percentage ash. In the tissues the plant inorganic substances arc posited in various forms, often in combination with or ganic acids constituting some the proximate principle? the plant sometimes they are deposited in the ceil walls, in the form small crystals, or the whole cell-wal may loaded with inorganic material that will tain its shape even when the organic materials have been destroyed, as in diatoms, or in the epidermis Equisetum, in which silica deposited. Or lime-salts are deposited in the interior the cell, in the protoplasm either in single crystals, as in the epidermal cells onion peel, or in bundles long slender crystals, as in the stem lilies or fuchsia, or in skunk cabbage, when they are called raphides, writing customer a Latin word meaning needles or the crystals may in stellate Aggregations, as In the oxalate lime crystals rhubarb, shown in the last illustration. Protoplasm an indispensable part the cell-contents every living cell, but little interest the student pharmacognosy, who mainly concerned with those substances which have definite farin when seen under the microscope.

 

 

 

 

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