. Text-book of botany, morphological and physiological. Botany. FILICINE2E. 429 especially striking, from their great numbers and from being frequently flat and leaf- like ; the younger leaves are generally entirely covered and concealed by them. After these preliminary particulars, we may now turn to a consideration of the mode of growth of the separate organs. The growing end of the stem sometimes far outruns the point of attachment of the youngest leaves, and then appears naked, as in Polypodium vulgare, P. sporodo- carpum, and other creeping Ferns, as well as in Pteris aquilina, where, acc
. Text-book of botany, morphological and physiological. Botany. FILICINE2E. 429 especially striking, from their great numbers and from being frequently flat and leaf- like ; the younger leaves are generally entirely covered and concealed by them. After these preliminary particulars, we may now turn to a consideration of the mode of growth of the separate organs. The growing end of the stem sometimes far outruns the point of attachment of the youngest leaves, and then appears naked, as in Polypodium vulgare, P. sporodo- carpum, and other creeping Ferns, as well as in Pteris aquilina, where, according to Hofmeister, it frequently attains in old plants a length of several inches without bearing leaves. Mettenius states that in many Hymenophyllacese leafless prolon- gations of the axis of this kind have been taken for roots. In other cases, on the contrary, especially in Ferns with an erect growth, the increase in length of the stem is much slower, its apex remaining enclosed in a leaf-bud. The stem generally ends in a flat apex; sometimes, as in Pteris^ it is even imbedded in a funnel-shaped elevation of the older tissues (Fig. 301, E). The apex of the stem is always occupied by a clearly distinguishable apical cell, which is either divided by walls alternately inclined, and then resembles, when viewed from above, the transverse section of a biconvex lens; or it is a three-sided pyramid, with a convex anterior surface and three oblique lateral surfaces, which intersect behind. The outlines of the segments, which are in the first case in two, in the second case in three rows, or arranged with more complicated divergences, soon disappear in conse- quence of numerous cell-divisions and of the displacement caused by the growth of the masses of tissue and leaf-stalks surrounding the apex. The apical cell, for instance, of Pteris aqui- lina, is wedge-shaped, the segments on the horizontal stem forming a right and a left, row; the edges of the apical cell face upwards and dow
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1882
