. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 86 FOEMS OF SIMPLE LEAVES. sist of one or more leaflets (foliola) separately attached to the petiole or leaf-stalk (fig. 156). In a single leaf the blade may be either' attached to a petiole or sessile on the stem; while in a compound leaf the blades or leaflets are separately attached to the petiole. In the earliest stage of growth aU leaves are simple and undivided, and it is only during the subsequent development that divisions appear, which may commence at the base
. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 86 FOEMS OF SIMPLE LEAVES. sist of one or more leaflets (foliola) separately attached to the petiole or leaf-stalk (fig. 156). In a single leaf the blade may be either' attached to a petiole or sessile on the stem; while in a compound leaf the blades or leaflets are separately attached to the petiole. In the earliest stage of growth aU leaves are simple and undivided, and it is only during the subsequent development that divisions appear, which may commence at the base or at the apex of the leaf The forms which the difierent kinds of simple and compound leaves assume are traced to the character of the venation, and to the amount of parenchyma produced. SiSiPLE Leaves.—When the parenchyma is developed symme- trically on each side of the midrib or stalk, the leaf is equal (fig. 164); if otherwise, the leaf is unequal or oblique (fig. 151), as in Begonia. If the margins are even and present no divisions, the leaf is entire (irir- teger), as in figs. 164 and 165; if there are slight projections of cellular or vascular tissue beyond the margin the leaf is not entire (fig. 151); when the projections are irregular and more or less pointed, the leaf is dentate or toothed (fig. 170); when they lie regularly over each. Fig. 164. Fig. 165. Fig. 166. Fig 16r. Fig. 158. Fig. 15B. other, like the teeth of a saw, the leaf is seirate (figs. 151,169); when they are rounded, the leaf is crenate (fig. 174). If the divisions extend more deeply than the margin, the leaf receives different names accord- ing to the nature of the segments: thus, when the divisions extend about half-way down (figs. 149,159), it is cleft (fissus), and its lines of separation are called fissures (fissura, a cleft); when the divisions extend nearly to the base or to the midrib (fig. 185), the leaf is partite, and its lines of separation are called partitions. These divisions take pla
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
