METAMORPHOSIS OF ORGANS, in botany, a subject of so much importance that it has been exalted to the rank of a distinct branch of botanical science, under the name of morphology or vegetable marphology. Attention to it is essential to a philosophical study of botany; yet it may almost be said that nothing was known either of its facts or its laws till the poet Goethe proclaimed them to the world in his treatise entitled Die Meta moiphose der Pflanzen in 1790. Linnreus had, indeed, called attention to the develop ment of organs, and the changes which they undergo, and had made this the Rubject of a thegiS entitled Prolepsis Plantarum in 1760; but, in a manner very unusual with him, he mixed up with his observations and philosophical speculations certain fanciful supposi tions, the falsehood of which soon becoming apparent caused all the rest to be neglected. Wolff aftetwards extricated the true from the fanciful in the views of Linnaeus, and gave them greater completeness; but he introduced the subject only incidentally in a paper on comparative anatomy, which failed to attract the attention of botanists, and probably had never been seen by Goethe, whose discovery, apparently altogether original, is one of the finest instances on record of acute observation combined with philosophical gen eralization.
The metamorphosis of organs is noticed in the articles on particular organs. It is only necessary here to make a very general statement of its facts and laws. A plant is composed of the axis and its appendages; the axis appearing above ground as the stem and branches, below ground as the root; the appendages being. entirely above ground, and essentially leaves; all organs which are not formed of the axis being modified leaves. The proof of this consists very much in the gradual transition of one organ into another, manifest in some plants, although not in othem; as of leaves into bracts, onc of the most frequently gradual transitions; of leaves into sepals, as seen in the leaf-like sepals of many roses; of sepals into petals, as seen in the petal-like sepals of lilies, crocuses, etc.;
of petals into stamens, as seen in water-lilies; and even of stamens into pistils, often exemplified in the common house-leek. The proof is confirmed and completed by obser vation of the monstrosities which occur in plants, particularly in the frequent return of some part of the flower to its original type, the leaf, and in the conversion of one past of the flower into another, which is often the result of cultivation, and is particularly illustrated iu double flowers, the increase of the number of petals being the result of the conversion of stamens into petals.
A flower-bud being a modified leaf-bud (see Bun), and a flower therefore the develop ment of a modified leaf-bud, the parts of a flower correspond in their arrangement with the leaves on a branch. But peculiar laws govern the development of organs in each species of plant. Thus the leaves in one are opposite; in another, alternate; in another, whorled; all depending on the law which governs the growth of the axis in relation to the development of leaves, which is very constant in each species; and in like manner the parts of the flower are developed in whorls around an abbreviated terminal portion of the axis, the energies of the plant being here directed to the reproduction of the species, and not to the increase or gowth of the iudividual. The fruit itself, being formed from the pistil, is to be regarded as formed of niodthed leaves.' Goethe truly says: " The pod is a leaf which is folded up and grown together at its edges, and the capsule consists of several leaves grown together; and the compound fruit is composed of several leaves united round a common center, their sides being opened so as to form a communication between them, and their edges adhering together." The metamorphosis of organs has been investigated with great diligence and success, and beautifully elucidated by Miguel, Lindley, Schleiden, and other botanists.