Page:The Botany of the Antarctic Voyage.djvu/392

356 berry, twining branches, and differently nerved leaves, in all which respects it is more evidently a genus of Smilacetz, than either Callixene or Pkilesia. There is no reason for supposing Doinbey's Capia to be other than Lapageria rosea.

It appears to me to be through these Antarctic and extra-tropical American genera, together with the Callixene of New Zealand and Drymophila of Tasmania, that the Smilacea, Lindl., are inseparably connected with the Tribe Asparagea, Lindl., of LUiacece; groups which Dr. Lindley has placed in separate natural classes, on the ground chiefly of anatomical differences in their stems: and it further appears that all modifications of a stem typical of Endogens and one equally characteristic of Dictyogens may be traced amongst these plants.

My own observations on the wood of P/tilesia do not exactly lead to the conclusions that the learned author of the 'Vegetable Kingdom' has formed; what appears to be bark is at no period separable from the subjacent wood, and the pith is of undefined form. There is a resemblance between the bark of Pkilesia and that of an exogenous stem, but it is apparent and not real : the stem consists of one mass of cellular tissue, through which bundles of vascular tissue descend, between the axis and the cuticle ; abundantly towards the latter, where they all coalesce, though always at a little distance within the circumference; more sparingly towards the axis, where a space is often left wholly unoccupied with woody fibres. A transverse section of such a stem thus presents, 1st, a cuticle; 2nd, a zone of cellular tissue, often formed of thick walled cells ; 3rd, a zone of wood, dense and defined externally, gradually laxer towards the axis and separating into bundles which irregularly surround a central column of pith. The only difference, in short, between this and any other Endogenous stem, consists in the first-formed or outer bundles being disposed more symmetrically, and being combined into one zone.

If a branch of Luzuriaga radicans be examined, the same peculiarity will be perceived, with only this difference, that the zone of wood is narrower and the pith broader. In Callixene pohjphylla, the woody zone, though still continuous, is narrower still. In C. parviflora both its edges (both inner and outer circumference) are clearly defined ; and in C. marginata it is sometimes interrupted. The Callixene marginata thus shows this disposition of the outer vascular bundles to unite in the lowest degree of these South American Smilacece, but in Lapageria the same tendency will be found in its highest, for the stem f that plant is almost wholly composed of woody matter, concentrated externally into a well-defined zone, rather lootc-i towards the centre, and enclosing large trachea; with very little cellular tissue intermixed. Externally to the wood is a very narrow layer of condensed parenchyma. In the first year's twig of this plant, the cellular tissue is proportionably abundant, with separate vascular bundles scattered through it, but is absorbed or obliterated afterwards. Nor is it in the genera of South America alone that these woody bundles are thus arranged, it is so in the Geitonoplesium {Luzuriaga cymosa, Br.) of New Holland, and in Drymophila, Br. ; and even nearer home in Convallaria and probably in many Convallariea. To the last mentioned group the above named genera most assuredly belong j whether the venation be parallel as in Callixene, parallel and retose between the costae as in Lapageria, or wholly retose as that of Pkilesia appears to be, from the two lateral of the three parallel costse forming the thickened margin of the leaf.

On the other hand, if we turn to the Smilacea proper, as limited by Dr. Lindley, even they display no more deviation from the common Endogenous structure than do the Convallariea: A young shoot of Rkipogonmn shows the same disposition of the woody and cellular tissue as Callixene polypkylla, with rather a broader zone of cellular tissue surrounding the wood ; but in an older stem of the same, the wood so predominates over the parenchyma, that the zone of cellular tissue is only distinguished with difficulty. In the Sniilax excelsa, L., of Em-ope, the woody zone of the young branch is neither so continuous nor regular, but it becomes so in the older state of the plant. Tamus communis presents the same arrangement. In the young stem of Testitdinaria. elepkantipes I do not find the medullary plates described by Dr. Lindley ; there appears to me to be a broad and perfectly continuous zone of wood, sending six or eight prolongations towards the axis, where there are further a few irregularly disposed bundles. I shall conclude this long digression by instancing the genus Jnncus as of the furthest removed from