Abstract
Plant fibres are elongated cells, that is, grown objects whose structure can only be fully understood from a development point of view. The young differentiating fibre cell has a very thin wall, consisting of an amorphous matrix of pectic and hemicellulosic material reinforced by only a few percent of cellulosic microfibrils. Curiously enough, this percentage (say, 5 percent by volume) corresponds approximately to the amount of iron rods in reinforced concrete! The microfibrils with a diameter of about 250 Å are arranged in a dispersed interwoven texture (Fig. 6). This so-called primary wall contains in the living cell some 90 percent. of water and, of the technically important dry matter, only less than half is cellulose, which alone is left over in the macerated preparations for the electron microscope. The growth of the primary wall consists in a widening of the existent texture combined with a continuous neoformation of new wall lamellae (multi-net growth) . The differentiation of pit fields and bordered pits occurs during this growth. The pit areas no longer increase their surface, though their distance may still considerably increase (mosaic growth, Fig . 5).
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