. Botany for high schools and colleges. Botany. 374 BOTANY. cliyma, or fibrous tissue), tUe stems are frequently very liard. The fundamental tissues frequently develop a good deal of mucilaginous or slimy matter. Both stems ami roots develop from a tbree-slded apical cell. The apical cell of the root continually undergoes fission not only parallel to its sides, but also parallel to its base—, at right angles to the axis of the root. The daughter-cells thus cut off {k, k, Fig. 257a) constitute the root-cap (pileor7dza) with which each root-tip is covered. The leaves, which unfold circinatel
. Botany for high schools and colleges. Botany. 374 BOTANY. cliyma, or fibrous tissue), tUe stems are frequently very liard. The fundamental tissues frequently develop a good deal of mucilaginous or slimy matter. Both stems ami roots develop from a tbree-slded apical cell. The apical cell of the root continually undergoes fission not only parallel to its sides, but also parallel to its base—, at right angles to the axis of the root. The daughter-cells thus cut off {k, k, Fig. 257a) constitute the root-cap (pileor7dza) with which each root-tip is covered. The leaves, which unfold circinately, are often very large, and in most eases are more or less lobed and divided, frequently becoming several times compound. Their development is slow, the rudiment of the petiole formino; one year, and that of the blade the next, while the opening or unfolding does not take place till the following year. The growth is sometimes periodic, as in Oleiehenia and Lygodium. In the. Fio. 2S8. Pig. 8S9. Fig. 260. Fig. 268.—Tinder side of a fertile leaflet of Aspidiwrn FUix-mas, with eight Bori. i, the indusium. Magnified.—After Sachs, Fig. 259.—A leailet of Asplmium, showing the elongated Bori, each covered hy a laterally placed Indusium.—From Le Maout and Decaisne, Fig. 260.—A leaflet of Adiantum. Bhowing the sori covered by indusla formed by reflexions of the margin of the leaflet.—From Le Maout and Decaisne. latter the leaf eventually becomes greatly elongated, resembling a climbing stem. The sporangia are usually formed in clusters {sori) on the veins, on the under side of the leaves, or upon their margins. The sori may bH distinct and rounded or more or less elongated, or they may be confluent over considerable portions of tlie surface. In some cases the sori are naked (as in Fig. 2576), but quite frequently each one is covered by a cellular outgrowth of the leaf, called the indwAum (Figs. 358, 259, 360). In some cases the indusium is shield-shaped, its short pedicel
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1885
