. Plants and their uses; an introduction to botany. Botany; Botany, Economic. THE FERNS 537 the lowest cell gives rise to the first leaf. A later stage in the de- velopment of these parts is shown in Fig. , B. Covering the growing tip of the root, somewhat as a thimble covers a finger tip, is a protective organ termed the root-cap. Such a thimble-like cover- ing continually renewed by the meristem which it protects is char- acteristic of true I'oots. Root-hairs for absorption are soon devel- oped. The leaf (Figs. 365, B, 362, B) soon differentiates into petiole and blade, and cur^-es so as
. Plants and their uses; an introduction to botany. Botany; Botany, Economic. THE FERNS 537 the lowest cell gives rise to the first leaf. A later stage in the de- velopment of these parts is shown in Fig. , B. Covering the growing tip of the root, somewhat as a thimble covers a finger tip, is a protective organ termed the root-cap. Such a thimble-like cover- ing continually renewed by the meristem which it protects is char- acteristic of true I'oots. Root-hairs for absorption are soon devel- oped. The leaf (Figs. 365, B, 362, B) soon differentiates into petiole and blade, and cur^-es so as to drag the tender leaf-tip up out of the ground. An extreme curvbig of this nature performed by t'very. Fig. 363.—Fern Antheridium iPtcris i/;.. Polypody Family, Polypodiacew), "i". (Lucrssen.) Fig. 364.—Fern Archegonium {Osmunda . Royal-fern Family, Osmunda- ceai). A, first stage viewed from above, ^^-. B, same, cut vertically to show the central cell (c) from which the egg is formed, and the cells (h) which give rise to the neck, i;!". C-E, older stages, showing canal cells (Ac, 6c). F, neck with mouth closed. G, same, top view, /f, same, mouth open. /, same as E but w'ith egg-cell (f) ready for fertilization. (Luerssen.) branch of the developing leaves gives us the familiar crozier-Iike vernation characteristic of ferns. In the axis of the stem soon ap- pears a central cylinder of prosenchyma which developing also in the root and the leaf serves as a channel for conducting solutions absorbed bj^ the root to the green food-making parts of the leaf, and likewise dissolved nutrients from the leaves to the stem and the root where they may be used in growth or stored as a reserve. As the stem grows larger, and leaves and roots become more numer- ous, its central cylinder becomes a hollow cylindrical net-work of broad fiat meshes (Fig. 366), giving off slender branches to the. Please note that these images are extracted from scanned page images that may ha
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