Introduction to structural and systematic botany, and vegetable physiology, : being a 5th and revedof the Botanical text-book, illustrated with over thirteen hundred woodcuts . ily, &c. Occasionallythe ribs of a radiated-veined leaf converge and run to the apex of theblade, as in Rhexia and other plants of the same family, thus resem-bling a parallel-veined or nerved leaf; from which, however, it isdistinguished by the intermediate netted veins. But when the ribsare not very strong, such leaves are frequently said to be nerved,although they branch before reaching the apex. 280. According to th
Introduction to structural and systematic botany, and vegetable physiology, : being a 5th and revedof the Botanical text-book, illustrated with over thirteen hundred woodcuts . ily, &c. Occasionallythe ribs of a radiated-veined leaf converge and run to the apex of theblade, as in Rhexia and other plants of the same family, thus resem-bling a parallel-veined or nerved leaf; from which, however, it isdistinguished by the intermediate netted veins. But when the ribsare not very strong, such leaves are frequently said to be nerved,although they branch before reaching the apex. 280. According to the theory of De Candolle (275), the shapewhich leaves assume may be viewed as dependent upon the dis-tribution of the veins, and the quantity of parenchyma; the gen-eral outline being determined by the division and direction of theveins ; and the form of the margin, (whether even and continuous,or else interrupted by void spaces or indentations,) by the greater or FIG. 231-244. Various forms of simple leaves. THKIR FORMS. 157 less abundance of the parenchyma in which the veins are distrib-uted. This view is readily intelligible upon the supposition that a 245 247 248. /V~-JSt~~. leaf is an expansion of soft parenchyma, in which the firmer veinsare variously ramified. Thus, if the principal veins of a feather-veined leaf are not greatly prolonged, and are somewhat equal inlength, the blade Avill have a more or less elongated form. If theveins are very short in proportion to the midrib, and equal in length,the leaf will be linear (as in Fig. 240) ; if longer in proportion,but still equal, the leaf will assume an oblong form (Fig. 242),which a slight rounding of the sides converts into an oval or ellip-tical outline. If the veins next the base are longest, and especiallyif they curve forward towards their extremities, the leaf assumes alanceolate (Fig. 239), ovate (Fig. 241), or some intermediate the other hand, if the veins are more developed beyond the mid-dle of the blad
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Keywords: ., bookauthorgra, bookcentury1800, bookdecade1860, booksubjectbotany
