It would be as useless as it would be wearisome to follow out in detail to its extremest point of absurdity the progressive transformation which the doctrine of metamorphosis underwent in the hands of the botanists of the nature-philosophy school, and to see how its catchwords, polarity, contraction and expansion, the stem-like and the fistular, anaphytosis and life-nodes, and others, were compounded with the results of the most every-day observation into meaningless conglomerates; rough obscure impressions of the sense, as well as incidental fancies, were regarded as ideas and principles. A full account of these inconceivable aberrations is to be found in Wigand’s ‘Geschichte und Kritik der Metamorphose.’ Our own countrymen certainly, Voigt, Kieser, Nees von Esenbeck, C. H. Schulz, and Ernst Meyer (the historian of botany) bear off the palm of absurdity, but there were others also, among them the Swedish botanist Agardh, and some Frenchmen, Turpin, for instance, and Du Petit-Thouars[45], who were not altogether free from this weakness. Even the best German botanists of the time, such as Ludolph Treviranus, Link, G. W. Bischoff, and others, managed to escape the influence of this philosophy of nature, only where they confined themselves to the most barren empiricism. Strange phenomenon! that as soon as gifted and understanding men began to talk of the metamorphosis of plants, they fell into senseless phrase-mongering; Ernst Meyer, for instance, was it is true no great botanist, but he shows in his ‘Geschichte der Botanik’ that he possessed a clever and cultivated intellect. The painful impression, which the treatment of the doctrine of metamorphosis by these writers makes upon us, is due partly to the fact that the deeper meaning of the idealistic philosophy never attained to logical expression in their hands, and still more to their indulgence in an unmeaning play of phrases, combining the highest abstractions with the most negligent and rudest empiricism, and sometimes with utterly incorrect observations. Oken can claim the merit of more correct observation and greater philosophical consistency, and if we reject his views, yet his mode of presenting them has at least the pleasing appearance of more consequential reasoning. We perceive for the first time the full greatness of the debt which modern botany owes to men like Pyrame de Candolle, Robert Brown, von Mohl, Schleiden, Nägeli, and Unger, the latter of whom only slowly worked his way out of the trammels of the nature-philosophy, when we compare the literature of the doctrine of metamorphosis before the year 1840 with the present condition of our science, for which they paved the way.