. Botany of the southern states. In two parts. Part I. Structural and physiological botany and vegetable products. Part II. Descriptions of southern plants. Arranged on the natural system. Preceded by a Linnæan and a dichotomous analysis. Botany -- Southern States. 58 LEAVES. place in many other plants, and tlie occurrence differs in no respect from what happens in the production of twin apples and other similar formations, except in its uniformity, which De Candolle denominated constant accidents. Why it should uniformly occur, and only in the upper leaves, we are unable to explain by any sec
. Botany of the southern states. In two parts. Part I. Structural and physiological botany and vegetable products. Part II. Descriptions of southern plants. Arranged on the natural system. Preceded by a Linnæan and a dichotomous analysis. Botany -- Southern States. 58 LEAVES. place in many other plants, and tlie occurrence differs in no respect from what happens in the production of twin apples and other similar formations, except in its uniformity, which De Candolle denominated constant accidents. Why it should uniformly occur, and only in the upper leaves, we are unable to explain by any secondary cause with which we are acquainted ; but by examination of the leaves, we are irresistibly led to the conclusion, that the slight variation in the direction of the veins and the great development of the parenchyma are the causes of the phenomenon. The other leaves are of the oval lanceolate form, with the veins forming acute angles with the midrib ; but in the perfoliate leaves the veins pass oflf at nearly right angles, with a much more abundant production of the parenchyma, thus uniformly accomplishing in this case what occasionally happens in other vegetables. Perfoliate leaves occur, from the same cause, in the alternate varieties, by the union of the lobes, of what would otherwise form a cordate leaf, as in the Uvularia perfoliata. But the most singular variations produced by the operation of this cause, occur in the pitcher-like leaves. Our common Sarracenia (Side-saddle flower) is produced by the cohesion of the edges of the leaf, or, as it is most .generally supposed, of the petiole only, and the expansion at the top of the cup is thought to be the real lamina, which is probably the case. The Nepenthes or Pitcher-plant of India, presents a still more striking instance of variation, and partly from the cause und^ consideration. This singular leaf, ex- hibited in Fig. 92, rises from the stem with a round corn- Fig. Leaf of the pitcher-plaut. mon petiole, like
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