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Liber seen in the grape-vine, for example.
Liber usually means inner bark. The falling off the bork frequently leaves peculiar markinics or depressions, the latter sometimes decidedly conchoidal in shape, or the bork itself may appear in nodules or warts, or may peel off in more or less extended patches or flakes, any which conditions may serve as aids for recognition, the identity the several barks. In distinguishing between the barks stems and roots may also aided peculiar markings, traces former leaf-scars or more rarely the The middle bark consists mainly soft-walled parenchyma cells, which appear tangentially stretched in a transverse section. When cells which are not prosenchymatous in shape, that which are not long or fusiform, but nearly equal diameters in all how to buy a term paper directions, become thickened sclerogen layers, whether aggregated in large numbers as in the stones fruits or scattered among aurrounding parenchyma, these sclerenchyma cells are called stone cells a few such cells from a gritty particle in the flesh the pear are figured the preceding page, and the typical appearance sclerenchyma cells will readily recognized. Stone cells similar character are found in the middle bark various plants, either singly, scattered as in the Cinchonas or in large clusters or even in almost solid layers, as in the stone cells so-called star-cells from drug both in its whole and in its powdered condition, and course in differentiating between different harks the absence stone some cases as the presence them in other cases. Another feature the middle bark consists in the presence or absence, as the case may larger ducts, cells or spaces, latex-ducts, resin or oil cells or ducts, or air-spaces, etc. In fact cinchonas may grouped structural grounds into divisions based upon the presence or absence both stone-cells and The inner bark consists alternate wedges medullary rays which are narrow at the cambium zone and gradually widen and merge with the middle bark and bast portions fibro-vascular bundles which are widest at the cambium zone and gradually grow smaller and cease at the margin the middle bark in fact the demarcation between middle and inner bark an imaginary line uniting the outer points the bast bundles, as seen in a transverse The medullary rays consist cells similar or identical with those the middle bark both being fundamental tissne, but they are frequently elongated in a radial direction near the cambium zone, gradually becoming shorter in the radial direction until at or near the confluence with the middle bark the radial diameter less than the tangential diameter and the cells are tangentially stretched as in the middle bark The most characteristic features the inner bark are found in the bast or phloem portions. In the living plant this part actively concerned in the circulation the fluids and special ducts, english paraphrasing the so-called sieve-ducts, are here found. These ducts are formed elongated cells, which are separated partitions thickened material deposited in a sieve-like manner, the thinner parts, or meshes, consisting soft cell wall through which osmosis can take place readily.
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To the pharmacognocist these ducts are little or no importance, except that in the examination powdered barks the appearance fragments the sieve-like plates might possibly characteristic in Most essay writing services usa the bast consists parenchyma cells which are usually much smaller in diameter transverse section, but elongated in the direction the plant axis, therefore in a longitudinal direction. Some barks, however, contain also a large proportion prose neb ymatous cells or strings cells in the bast, which render the bark very tough, as in wild cherry, for example, may closely resemble the outer appearance the wood-cylinder as figured under woods in fact the structures phloem and In such cases the parenchyma the medullary faco the bark, especially if the hark too rigid curl or quill inwards.
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Drawing enlarged Still another and perhaps the most characteristic structures when present are the bast-cells, which are found in the phloem or bast. On transverse section these appear similar the stone cells the middle bark, aii seen in this figure bast-cells from calisaya bark, bat making a longitudinal section the bark these baet-cells are seen proaenchymatous in form, and they belong the mechanical tissue-ay stem, giving strength and eupi port. This shown in the longitudinal section from calisaya bark, shown the following page. The form, as well as the arrangement the bastcells, singly, in clusters, etc. may give peculiar appearance the section a bark in the transverse section calisaya bark, just shown, see the bastcells irregularly scattered, either singly or in quite email clusters while in the section cotton-root bark the baet-cells and bast-parenchyma are arranged in alternating layers, as shown.
Bastcells, therefore, are important diagnostic features in the determination tbe identity barks.
Most the parenchyma cells the middle and inner bark contain starch, as well as the various medicinally valuable ingredients like alkaloids, etc. Some barks contain special mucilage cells, which are usually larger than the other parenchyma cells, or special oil cells, which are sometimes smaller than the other parenchyma cells.
Alkaloids are contained in all the various cells, but probably mostly in the parenchyma the inner bark. The outer bark, even when formed necrosed tissues inner bark, ghostwriters for hire contains comparatively little medicinal value bid writing services and therefore generally rejected if present in the form bork but if not present as bork, constitutes part the drug and the whole bark used. We are now prepared study some facts in regard the coarse appearances bark, after which the principles classifying them will considered. It course well known that soft tissues fruits, etc. become darkened when exposed the oxidizing influence air a piece peeled apple becomes yellowish and eventually brownish in a very short time after the protecting epidermis has been removed and dried fruits almost all kinds are darker-colored than tbe fresh pulp or flesh the corresponding fruits.