Page:The Botany of the Antarctic Voyage.djvu/104

82 pallide flavo-brunnea, utrinque (chalaza apiceque) fusca, albumini appressa, exteriore remota ; inter has duas raphe saepius solutus apparet. Albumen carnosum. Embryo parvus, albidus, oblique tetragonus, in basi albuminis immersus, hilo proximus.

This species was, according to Lamarck, originally discovered by Commerson, who accompanied Bougainville in his voyage to the Straits of Magalhaens, &c. I have gathered it abundantly both in Tierra del Fuego and the Falkland Islands. In the latter locality it is very abundant, and had been previously detected by M. Gau- dichaud and by Admiral D'Urville. It is rare in Campbell's Island, and was not observed upon Lord Auckland's group. It is equally distinct from the R. grandiflora (Marsippospermum grandiflorum, Desv., Hook. Ic. Plant, t. 533) and from the following, in the elongated bractea which subtends the flower, as well as the size of the plant, form of the leaf and capsule, and curious structure of the seeds. I have no hesitation in retaining Lamarck's specific name of Magellanica for this plant, the species being well characterized by that author, and known to Desvaux at the time he established the genus Rostkovia ; this he did upon different grounds however from those which induce me to retain it.

M. Desvaux founds the genus on this solitary species, but grounds his generic character on an erroneous idea of the structure of the capsule, which he describes (Journ. de Bot. 1. c.) as "capsula globosa, uniloculars, non dehiscens; trophospermum suturale" (p. 326) ; and again in the previous page, "Je crois que la capsule ne s'ouvre point; par suite d'une observation generale, e'est que tout fruit qui n est point anguleux dans aucune de ses parties, n est pas dehiscent, surtout s'il est sphérique les graines en grand nombre sont disposees sur trois trophospermes (placentae) fixes sur les parois de la capsule et alternant avec les indices de dehiscence qui s'aper^oivent au milieu des parois des loges, et qui sont toujours indiques, malgre que cette dehiscence n'ait point lieu dans quelques genres de la famille des Joncinees" (p. 325). The capsule of R. Magellanica I have described as of a very hard consistence, and its dehiscence does not take place until a considerable period after the apparent ripening of the seeds ; that it does burst is however abundantly evident, and the dehiscence takes place by three valves, exactly as in Desvaux's genus Marsippospermum and in other Juncece, the placentae occupying the axis of the valves. From the above extract I conclude that M. Desvaux did not examine fully ripe capsules, and took the groove at the back of the valves, which is seen in almost all Junci, denoting the position of the placenta, for the line of dehiscence. In the work alluded to no description of the seeds themselves is given, though another genus is founded on a supposed peculiarity of structure in that organ. Mr. Brown (Piodr. p. 258), in his observations on the genus Juncus, remarks that no dependence is to be placed on the form of the testa as a generic character, "nee secernendae eae seminibus scobiformibus, testa nempe, quae in pluribus utrinque laxa, in his valde elongata;" and as in the genus Juncus itself there are several forms of that organ, so in Rostkovia, as it now stands, it differs remarkably in two of the species. In R. grandiflora the outer integument of the seed is lax and drawn out at both ends, as in Juncus castaneus, Sm., and several other species; but in the R. Magellanica it assumes a form which I have not seen in any other species of the Natural Order, forming a very thick, even seed-coat, hard, smooth and shining externally, marked on one side with a prominent ridge, indicating the position of the raphe; within it is soft and spongy, with a large cavity. Inside this the nucleus hangs loose, suspended by the vessels of the raphe, which are more or less detached and often quite separate from the walls of the seed-coat, except at the base. The inner membrane immediately surrounds the albumen ; it is thin and membranous, obscurely striated or reticulated, of a pale brown colour with a broad orbicular dark-coloured chalaza at the summit and another dark spot and apiculus at the pendent apex. This membrane is quite free from the outer, and analogous to what is generally considered as the testa in many Junci which are described as not having that organ scobiform, but in which the true outer membrane of the seed, analogous to the coriaceous one of the present species, is delicate and hyaline, either altogether deciduous or leaving a few filamentous residua round the base and apex of the seed, or as in J. scheuchzerioides, leaving the raphe as the only attachment between the seed and placenta. In some species of the Order this outer membrane forms with water a transparent jelly, in which the seed appears immersed ; it is very similar to what is seen surround-