. The classification of flowering plants. Plants. 224 FLOWERING PLANTS In many Bamboos and a few other broad-leaved tropical grasses the blade is separated from the sheath by a petiole (fig. 113, A); but in most cases the blade follows directly on the sheath. The sheath is slightly prolonged above the point of union to form the ligule, which is generally a delicate membranous structure, varying much in length and form in different genera, and affording useful systematic characters (figs. 89-92). It may be represented by a line of hairs or reduced to a mere ridge, or even be absent. The blade i
. The classification of flowering plants. Plants. 224 FLOWERING PLANTS In many Bamboos and a few other broad-leaved tropical grasses the blade is separated from the sheath by a petiole (fig. 113, A); but in most cases the blade follows directly on the sheath. The sheath is slightly prolonged above the point of union to form the ligule, which is generally a delicate membranous structure, varying much in length and form in different genera, and affording useful systematic characters (figs. 89-92). It may be represented by a line of hairs or reduced to a mere ridge, or even be absent. The blade is usually long and narrow, linear or linear- lanceolate, often tapering to a long, fine point. In a few tropical grasses it is broad, as in Olyra, Pharus and others ; the genus Fhyllorachis from Angola has sagittate leaves. In. Fig. 95. Fig. 93. Transverse section of the leaf-blade of Festuca ovina, x 15. Fig. 94. Transverse section of the leaf-blade of F. ovina, var. rubra, x 35. Fig. 95. Transverse section of the blade of an upper leaf of F. ovina, var. nibra, x35. All from Ward. some species of Setaria the broad blade is plicately folded in the bud. The venation is with few exceptions parallel. The tissue is often raised above the veins, forming longitudinal ridges, generally on the upper surface (fig. 95); the stomata are developed in lines in the intervening furrows; the guard-cells are generally protected by two larger projecting secondary cells. The adult blade is often more or less twisted, frequently so much so that the upper and under sides become reversed when the stomata are situated only upon the originally upper side. In dry-country grasses the blades are often folded or rolled up. This rolling may be effected by bands of large wedge-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Rendle, A.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1904
