. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. VESSELS 35 Raphia} Moreover, fibres treated in various ways are the source of wood-pulp and other paper-making materials. The main function of vessels (Fig. 17) is water-conduction, but they also are elements of mechanical importance on account of their thick walls. These are necessitated by the frequent existence of negative pressures in the water-conducting Fig. 17.—Vessels showing various types of thickening and perforation. A, spiral ; B, annular ; C, portion of A in longitudinal section showing
. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. VESSELS 35 Raphia} Moreover, fibres treated in various ways are the source of wood-pulp and other paper-making materials. The main function of vessels (Fig. 17) is water-conduction, but they also are elements of mechanical importance on account of their thick walls. These are necessitated by the frequent existence of negative pressures in the water-conducting Fig. 17.—Vessels showing various types of thickening and perforation. A, spiral ; B, annular ; C, portion of A in longitudinal section showing attachment of thickening to wall ; D, end of vessel of Alder (Alniis) showing ladder-like perforation ; E, vessel of Poplar (Populus) ; F, vessel of Oak (Quercics) ; G, reticulate vessel of Marrow [Ciiciir- bita). b., bordered pit ; p., perforations between segments of vessel. such as obtain, for instance, when transpiration is active. At these times collapse of the vessels, under the positive pressure exerted 'by the surrounding elements, is prevented by the rigidity of their walls. The type of thickening varies greatly, depending largety on whether the vessel is formed in a part of the plant that is still gro\ring or in one that has reached maturity. In the former case the thickening must be of such a nature as to ' Regarding cotton see p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Fritsch, Felix Eugene, 1879-; Salisbury, E. J. (Edward James), Sir, b. 1886. London, G. Bell and sons ltd.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpl, booksubjectplants
