ADHESION, in botany, the union of parts in a plant which are separate in other plants, or in the younger states of the same plant. What we are accustomed to consider parts of different nature only seem so in consequence of the way in which A. occurs. A leaf is said to be stem-clasping when its base partially surrounds the stem; while a stem which seems to pierce through the leaf is said to be perfoliate; but they differ only in this, that in the former the lobes at the base of the leaf embrace the stem without adher ing, while in the latter they not only clasp the stem, but grow together where their margins come in contact. The leaves of the pitcher plant, formerly thought to be special organs without analogy, are known to be leaves so rolled up that their margins have touched and adhered. Other leaves, growing from opposite sides of the stem, adhere because their bases are connate, as in the honeysuckle; and yet others grow in a whorl, or all round a stem upon the same plane, and adhere at their margins, forming a sheath in the calyx. All the sepals are often distinct, as in the buttercup; but they often also adhere by their edge And form a cttp, as in the cherry, In the corolla the petals are either all separate, as in the rose, or adhere by their edges, as in heaths. In the rose, the
stamens are all distinct from each other; in the geranium they slightly adhere at the base; in the mallow they adhere in a parallel tube; in other plants they grow into a com plete tube. Certain parts of the pistil are called carpels, each of which is a hollow body terminated by a stigma. These carpels are hollow, because they are formed of a fiat organ doubled up so that its edges conic in contact and adhere. Sometimes only one carpel is present, as in the cherry; sometimes several, as in the rose. In the nicella the styles of the carpels are all distinct; in the lily and the myrtle the styles adhere so com pletely that there seems to be but one. In the apple the calyx seems to grow from the top of the fruit. This is because the carpels adhere to the inside of the calyx, which grows with the fruit, and leaves its extremities in a withered state near the top of the carpels. In the cherry no A. takes place between the carpels and the calyx; and, con sequently, when the fruit is ripe there is no trace of the calyx upon the upper end of the drupe. In the raspberry the fruit slips like a thimble from the receptacle, because the carpels all adhere by their sides.
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