On the development of the cystocarp in the genus Galaxaura and the auxiliary cells in the order of Nemalionales
The genus Galaxaura can in several respects be classed among the most remarkable Florideae. It is not only — with Chantransia — the genus richest in forms of all the genera belonging to the order of Nemalionales, which has more than 70 described species, it also offers, both in its interior and its exterior organization, such a high differentiation, and a tissue specialization going so far, that, as the monographer of the genus, the late Professor F.R. Kjellman (1900), said: ”it may be difficult even in the great province of the Florideae to find forms with a higher or even as high a division of labour in the tissues of the shoot...“. Even if the number of species may actually diminish with further investigations, this is in a way connected with a peculiarity of organization, characteristic of the genus Galaxaura, namely that the sexual plant of a species has quite another anatomical structure of the cortical tissue than does the tetrasporic plant. This remarkable discovery was made by Howe (1917, 1918), who had had the opportunity of studying some species of Galaxaura in the West Indies, in their natural localities. This fact was not known of any Floridea at the time Kjellman wrote his monograph on this genus in 1900. Moreover, Kjellman had a quite different conception of the position of the tetraspores during the course of development of the Florideae than the one we have nowadays formed from the results of the cytological research. To Kjellman the tetraspores or, as he called them, the ”tetragonidia“, were a kind of propagation organ with the character of ”Nebenfruktifikation“, and thus not, as we must now regard them, the reproduction bodies of the diploid generation ending the diplophase in the alternation of generations. Thus, when Kjellman in his herbarial studies found forms of Galaxaura with otherwise similar organization but with quite a different cortical anatomy, it was quite natural that he described them as new species. One of the tasks of future taxonomical research will therefore be to combine such ”species“ of Kjellman as, in reality, are only the sexual and the tetrasporic generation of one and the same species. Naturally, this problem can only be solved by a botanist who has the opportunity of studying the development of the Galaxaurae in their native localities. Finally, only cultures will be really decisive. However, the number of species of Galaxaura will certainly be reduced.
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Svedelius, Nils. (1942). On the development of the cystocarp in the genus Galaxaura and the auxiliary cells in the order of Nemalionales. Blumea. Supplement, 2(1), 72–90.