Vegetable organography; or, an analytical description of the organs of plants / by Aug. P. de Candolle. Translated by Boughton Kingdon.

  • Augustin-Pyramus de Candolle
Date:
1839-1840
Catalogue details

Licence: Public Domain Mark

Credit: Vegetable organography; or, an analytical description of the organs of plants / by Aug. P. de Candolle. Translated by Boughton Kingdon. Source: Wellcome Collection.

    59/66 (page 45)
    ive have described in the preceding chapters, preserve the same form throughout its entire length?—The uncer¬ tainty on this subject has been caused by Mirbel, who admits the existence of mixed tubes (tubes mixtes)—that is to say, tubes which in different parts of their length may be dotted, striped, or spiral like a gun-screw. The same tube,” says he, “ exhibits successively these dif¬ ferent forms : a trachea of the stem may terminate at the root in a strangulated vessel—may become a false trachea at the knot at the base of a branch—may pass over this in the form of a dotted tube, and resume in the leaves or petals the form of a true trachea.” Almost all the anatomists who have wTitten since this opinion lias been published, have written against it, or at least against its general application : several acknowledge that they find some tubes which bear at the same time short and long stripes, so that it may be perhaps ad¬ mitted that annular and dotted vessels pass one into another, and in this very restricted sense the existence of mixed vessels may be admitted;—but the majority deny the other combinations. Rudolphi says, that he believes that it is impossible for an annular tube ever to change into a spiral vessel ; and he explains the assertion of Mirbel, in thinking that he has, unconsciously, passed from one vessel to another under the field of the micro¬ scope. Dutrochet, in particular, affirms that there are no mixed vessels, in the sense which Mirbel assigns to this word ; and that the tracheæ preserve their organiza¬ tion throughout their whole extent. Amici says, that he has never met with any vessels compounded of tracheæ and of tubes. The assertion of Mirbel, he adds, may perhaps be only a simple hypothesis : every one who has applied himself to the anatomy of plants, easily comprehends the impossibility of following the course of a vessel for so long a distance.