separately, has induced me to make it the subject of particular consideration. Unknown before the time. of Linnæus, and first placed in its true light by the venerable poet Göthe, it lay neglected for nearly thirty years, until, having been revived by Du Petit Thouars, De Candolle, Brown, and others, it has come to be considered the basis of all scientific knowledge of vegetable structure. It has been my wish to bring every subject that I have introduced down, as nearly as possible, to the state in which it is found at the present day; but, alas! tasks that are infinite can never be accomplished by finite means. While the MSS. has been going through the press, my table has been covered with works illustrating the fundamental principles of the science, of scarcely any of which has it been possible to make the slightest use. This I regret the more, as some of them are of high interest, especially with regard to Vegetable Anatomy. In the statements I have made, I have uniformly endeavoured to render due credit to all persons for the discoveries by which they may severally have contributed to the advancement of the science; and *The more important of these works are, Agardh, C. A., Lehrbuch der Botanik. Copenhagen, 1831. De Candolle, A. P., Physiologie Végétale, &c. Paris, 1832. Arnott, G. W. The article Botany in the Edinburgh Encyclopædia. Bischoff, G. W., Handbuch der Botanischen Terminologie und Systemkunde. Nuremberg, 1830. Annales des Sciences Naturelles, par MM. Audouin, Ad. Brongniart, et Dumas. Several Numbers. Mirbel, C.B., Mémoire sur le Marchantia. Paris, 1832. if I have on any occasion either omitted to do so, or assumed to myself observations which belong to others, it has been unknowingly or inadvertently. It is, however, impracticable, and if practicable it would not be worth while, to remember upon all occasions from what particular sources information may have been derived. Discoveries, when once communicated to the world, become public property: they are thrown into the common stock for mutual benefit; and it is only in the case of debatable opinions, or of any recent and unconfirmed observations, that it really interests the world that authorities should be quoted at all. In the language of a highly valued friend, when writing upon another subject: “The advanced state of a science is but the accumulation of the discoveries and inventions of many: to refer each of these to its author is the business of the history of science, but does not belong to a work which professes merely to give an account of the science as it is; all that is generally acknowledged must pass current from author to author."* London, Sept. 10. 1832. *Brett's Principles of Astronomy, p. v. 2. Of its External Modifications 3. Of its Internal Modifications 2. Of the Endogenous Structure |