On the forms and structure of fern-stems / by George Ogilvie.

  • Ogilvie, George
Date:
1859
Catalogue details

Licence: Public Domain Mark

Credit: On the forms and structure of fern-stems / by George Ogilvie. Source: Wellcome Collection.

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    observed also, that, even in Dicotyledons, a certain vegetative independence is indicated in the origin of rootlets, from the local application of moisture so fostering their production as to cause their development evmi from abnormal parts. It does not appear that the assumption of two distinct deve¬ lopments of vegetative power in the guise of leaf-buds and root¬ lets—or, as they might be termed, jjhyllophytons and rhizophy- tons,—is at all opposed to the analogy of other forms of organi¬ zation ; for we observe a coiTesponding diversity of individualized organs in various compound animals, as, for instance, in the alimentary, generative, and protective appendages of Ilydracti- nia, the polypes and avicularia of the Polyzoa, and the cirrhi and ovarian capsules of the Physograda,—parts whieh may certainly be assumed to be mere modifications of a common original form, but between which it would not be easy to point out much com¬ munity of structure in proof of such co-relative derivation. There still remains for consideration the arrangement of the dark-coloured tracts commonly regarded as of the nature of woody tissue; but for the present it may suffice to notice the great diversity which prevails in different species in the disposi¬ tion of these fasciculi. Thus, in Osmuyida we have an accumu¬ lation of dark tissue on the exterior of the caudex; in Blech- num horeale, again, it occupies the interior; in Pteris aquilina it forms broad bands interposed between an outer and inner layer of vascular tissue; while in Filix mas it exists onlv as a thin stratum ensheathing the latter; in Lastrxa dikitata it occurs in isolated masses in the cellular core of the rhizome. The author may remark, in conclusion, that but a few^ days ago his attention w^as called by a friend to an incidental notice —the only one he has yet met with—of the fibro-vascular system of Ferns, in a paper on Sigillaria in the ^Edinburgh Philosophical JournaP for 1844, by Mr. King of Newxastle, wdiich, from its geological title, he had previously overlooked. Mr. King^s re¬ marks, so far as they go, will be found quite in accordance with the foregoing. He surmises that in Tree-ferns (owing to the greater development of the longitudinal fasciculi) the regular rhomboidal meshes may be reduced to long narrow' slits. This is the more probable from an arrangement precisely of this kind obtaining in creeping rhizomes, such as those of the bracken. It is w’ell known to botanists that there is a similar diversitv in the extension of the medullary rays of Exogens : they are much larger, for instance, in the oak than in most other woods, and in the Clematis they reach the whole length of the internodes, so that, w'hon they decay, the stem breaks up by the separation of its component woody wedges.
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