Text-book of botany, morphological and physiological . y lying leaves, pieces of stick, and the like. Thesmall pressure from without clearly prevents in these cases the superficial growth ofthe walls of the cells with which these bodies are in contact, while the adjoining cellsextend laterally and enclose them. But the most remarkable illustration of this law is seen in the effect produced bya slight pressure on the growth of tendrils, the longitudinal growth of the cells beingthus gready hindered and sometimes even stopped, while the cells of the oppositefree side elongate rapidly, as is seen
Text-book of botany, morphological and physiological . y lying leaves, pieces of stick, and the like. Thesmall pressure from without clearly prevents in these cases the superficial growth ofthe walls of the cells with which these bodies are in contact, while the adjoining cellsextend laterally and enclose them. But the most remarkable illustration of this law is seen in the effect produced bya slight pressure on the growth of tendrils, the longitudinal growth of the cells beingthus gready hindered and sometimes even stopped, while the cells of the oppositefree side elongate rapidly, as is seen even at the first glance without measurement bymaking a longitudinal section of a tendril curling round a slender support. In whatway the slight pressure which acts in a radial direction, and is generally combinedwith friction, exerts an influence on the longitudinal growth is however entirely un-known. Very similar phenomena are exhibited by the primary and secondary rootsof seedlings (as Zea, Faba, and Pisum). If they are allowed to grow in a damp. Fig. 449.—Growth of the pollen-tube o^ Campanula rapunciiloides: Kp the pollen-grain;ps the pollen-tube closely applied to the stigmatic hair nh. locality, and the growing parts are made to press on one side some solid body as apin or another root, the root bends like a tendril round the body with which it is incontact, this side growing more slowly than the opposite one. It is evidently inconsequence of a similar influence of pressure on growth that the aerial roots ofAroideae and Orchideae become closely attached to solid bodies, following exactlytheir inequalities. But even unicellular tubes, such as the hyphae of Fungi andpollen-tubes (Fig. 449) are induced by contact with a solid body to grow closelyapplied to it. In this simplest case, where the hydrostatic pressure is uniformover the cell and distends the cell-wall, it does not admit of a doubt that the pressurefrom without impedes the growth of the cell, independently of
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
