DUDRESNYA. tig 



development of the spore fruit from the egg-cell. Such a doctrine 

 has, of course, the value of mere conjecture only. 



The fusion nucleus increases in size and shows clearly a single large 

 nucleolus and a well-defined threadwork in which are held distinct 

 chromatin granules. The trichophore now begins to send out one or 

 more protuberances (Fig. 46, E). The fusion-nucleus divides, and 

 one of the daughter-nuclei passes into a protuberance which is then 

 cut off by a transverse wall. By a repetition of this process many 

 cells are produced, each containing a nucleus which is a descendant of 

 the fusion-nucleus. Each of the cells thus borne by the carpogonium 

 will give rise to gonemoblast filaments, whose end cells form the 

 carpospores. 



DUDRESNYA. 



From the foregoing it will be seen that the sexual process and the 

 subsequent development of the fecundated egg in Batrachospermum 

 are comparatively simple, but in the vast majority of the Rhodophycece, 

 because of the peculiar structure of the thallus, the details in these pro- 

 cesses are extremely difficult to follow even in the most favorable cases. 



In the better known representatives, such as Dudresnya and the 

 simpler Callithamnion, the carpogonium does not give rise to the 

 spore fruit (cystocarp), as in Nemalion (Wille) and Batrachosper- 

 mum, but from each carpogonium whose egg-cell has been fecundated 

 a number of filaments (two or three in Dudresnya) are developed, 

 which fuse with certain vegetative cells, and from which, in connection 

 with a part of the filament, the cystocarps are developed. These fila- 

 ments are the ooblastema filaments of Schmitz ('83) and the sporo- 

 genous filaments of Oltmanns ('98). The vegetative cells with 

 which these fuse are known as auxiliary cells or brood cells. This 

 fusion of the sporogenous filaments with auxiliary or brood cells was 

 regarded by Schmitz and his followers as a second fecundation, a 

 phenomenon unparalleled among plants, and which, as Schmitz put it, 

 was contrary to all tradition : " Einen zweimaligen Befruchtungsact 

 im Entwickelungskreise einer einzelnen Species anzunehmen, dagegen 

 straubt sich zur zeit die botanische Anschauung vollstandiger, das 

 widerspricht aller Tradition." 



The recent researches of Oltmanns ('98) seem to show what is, in 

 all probability, the true significance of the fusion of sporogenous fila- 

 ments and auxiliary cells. He maintains that the fusion of the sporoge- 

 nous filament, or a cell of the same, and an auxiliary cell is not a 

 sexual process, since it is only a cytoplasmic and not a nuclear fusion 

 that takes place. Furthermore, the nuclei of the carpospores, as in 



