. A class-book of botany, designed for colleges, academies, and other seminaries where science is taught ... Illustrated by a flora of the northern United States particularly New England and New York. Botany; Plants -- United States; Plants -- Canada. 86 THE LEAF. are always connected by simple transverse veinlets. Ex. grass, lily. 1 2 3 4. FIG. 28. — Forms of venation. J, 2, Exogens; 3, Endogen; 4, acrogen. 3cl. Forked-veined, as in the , when the veins divide and subdivide by forked divisions wliich do not unite again. Ex. ferns. 230. Of the first Idnd of venation, the reticulate
. A class-book of botany, designed for colleges, academies, and other seminaries where science is taught ... Illustrated by a flora of the northern United States particularly New England and New York. Botany; Plants -- United States; Plants -- Canada. 86 THE LEAF. are always connected by simple transverse veinlets. Ex. grass, lily. 1 2 3 4. FIG. 28. — Forms of venation. J, 2, Exogens; 3, Endogen; 4, acrogen. 3cl. Forked-veined, as in the , when the veins divide and subdivide by forked divisions wliich do not unite again. Ex. ferns. 230. Of the first Idnd of venation, the reticulate, there are two varieties which desenc the most careful attention. The fealhcr-vdned and the radiate-veined. 1. The feather-veined leaf is that in which the venation con- sists of a midrib, giving off at intervals lateral veins with branching veinlets. Ex. beech, chestnut. 2. In the radiate-veined, the venation consists of several nerves (ribs) of nearly equal size, radiating from the base towards the circumference, each with its own system of veins and veinlets. Ex. maple, crow-foot. 3. In parallel venation, the veins are either straight, as in the linear leaf of the grasses, curved, as in the oval leaves of tlie Orchis, or transverse, as in the Canna, Calla, &c. §4. FORM OR FIGURE. 231. That infinite variety of beautiful and graceful forms for which the leaf is distinguished, becomes intelligible to the student only when viewed in connection with its venation. Since it is through the veins alone that nutriment is conveyed for the development and extension of the parenchj-ma, it follows that there -vvill be the greatest extension of outline where the veins are largest and most numer- ous. Consequently, the fonn of the leaf will depend upon the direction of the veins, and the vigor of their action, in developing the intervening tissue. For this interesting II1C017 we are indebted to Alphonse Dc Please note that these images are extracted from scanned page imag
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Keywords: ., bookcentury1800, bookdecade1840, bookpublisher, booksubjectbotany
