Page:The Botany of the Antarctic Voyage.djvu/327

Falklands, etc.] authors offers any explanation of their true nature. Poeppig describes several species, and, trusting more to a theoretical opinion of their origin, than to a careful analysis of the parts, or the definitions of De Candolle and Guilleinin, he misapprehends the structure of the ovarium, considering it to be a compound body, made up of three carpels combined, and of the plumose filaments, which are described in the generic character as Setae hypogynae alternating with the ovaria, and in the observations on the genus are doubtfully called Staminodia. Lastly, Endlieher regards the single ovarium as compounded of six, enclosed in a three-parted involucre, three of them fertile and three sterile, the latter being the plumose filaments.

The female flower of Myzodendron consisting of a solitary ovarium, enclosed in the adherent tube of the calyx, it is evident that the plumose setae must be a production of the calyx or ovarium. Their function and appearance resemble the pappus of Composite, and particularly of Valeriana in being only fully developed during the ripening of the seed. They cannot be compared with the four stout woody nerves of Tupeia Antarctica, which ascending from the pedicel, terminate in the sarcocarp of its berry in four sharp points that arch over an opening in the upper end of the endocarp of that plant, for the setas of Myzodendron contain no spiral vessels, and the true nerves of the calyx, though very obscure, may be traced in some of the species, as in M. brackystacliyum, where they appear alternating with the position of the setae (Plate CV. f. 11).

The tissue of which these setae are composed, is identical with what forms the sarcocarp of Tupeia and Viscum, namely, elongated viscid cells of great tenuity filled with a glutinous matter; in most Lorantliacear this tissue surrounds the endocarp and at an early period deliquesces into a homogenous viscid fluid, like that of Viscum. When looking over the plants of this order, in Dr. Lindley's herbarium, I remarked one whose ripe pericarp had burst during pressure and emitted a cottony substance; that gentleman liberally gave me specimens for examination, which showed the sarcocarp to be intermediate in its nature between that of Tupeia and of Myzodendron, being feathery and neither so deliquescent as in the former, nor elaborated into such a peculiar organ as in the latter.

The elaboration of these setæ, from cellular tissue, cannot be regarded otherwise than a very singular phenomenon, and, so far as my observations serve, it appears that it is merely the result of a rapid elongation of cellular tissue. The viscid substance, then, in this genus, instead of surrounding the endocarp, is confined within three fissures, and there collected into a terete or compressed body, which, escaping from its confinement, rapidly elongates from the growth of the cells which compose it, more than from the addition of new matter. The plumose appearance is caused by the separation of some of the utricles, which diverge on all sides in the species in winch the setæ are terete, or in their opposite margins when the latter are compressed. Of all the species, the setae of M. oblongifolium are the longest, and there are various gradations in length and tenuity between them and those of M. puuctidatuni. The M. Unearifolium, DC., has not only very long and slender filaments, but its whole endo-carp is at times surrounded with a feathery substance, which is thus not, as in its congeners, confined in loculi: when placed in water this feathery substance deliquesces. In M. imbricatum, Pœpp., the fissures of the pericarp are, according to the author of that species, filled with undivided stout obtuse filaments, collected together at the base, and never exserted.

I need scarcely allude to the fact, that the function performed by the gluten of Viscum and the feathery setae of Myzodendron is identical, though effected in a different way, and that it affords a singular instance of nature's employing the same means in a very dissimilar manner to the attainment of the same end. The viscid matter of