124 ASCOMYCETES AND RHODOPHYCE^fS. 



a transverse wall. This end cell continues the development of the 

 sporogenous filament, which in turn may fuse with other auxiliary 

 cells. At b, c, d the sporogenous parts of the fusion cells have given 

 rise to branches which will produce either sporogenous filaments or 

 spore fruits, as shown in Fig. 48, C, D. 



In all authentically known cases among the Rhodophycece the 

 structure of the female sexual organ, the carpogonium, or we may say 

 the oogonium, and the process of fecundation is essentially the same, 

 but the development of the cystocarps from the fecundated egg differs 

 widely in detail among the various genera. 1 So far as is known the 

 sporogenous filaments reach their highest development and complexity 

 in Dudresnya, in which, as we have seen, the fusion of each of the 

 sporogenous filaments takes place with a greater number of widely 

 separated auxiliary cells. In other forms, such as Callithamnion 

 and Dasya (Oltmanns, '98), in which only one or two closely situ- 

 ated auxiliary cells take part in the formation of the cystocarps, the 

 sporogenous filaments may consist of only a few cells at most. In 

 these cases we can scarcely speak of sporogenous filaments, but rather 

 of sporogenous cells. 2 



The relation which an auxiliary and a sporogenous cell sustain to 

 each other is somewhat different in the several known genera. As 

 already stated for Dudresnya, the sporogenous part of the fusion 

 cell (Fig. 48, B, C, D) gives rise to the cystocarp, while in Glceosi- 

 phonia capillaris (Oltmanns, '98) the sporogenous cell, after the 

 fusion of its contents with the auxiliary cell, may take no further part 

 in the development. Its cytoplasm and nucleus pass into the auxiliary 

 cell, and a cell-wall is formed separating the old cavity of the spo- 

 rogenous cell from the auxiliary cell. From the auxiliary cell the 

 cystocarp is now developed. A similar process takes place also in 

 Callithamnion and Dasya. Although the behavior of the two cells 

 in the last two genera named suggests a greater similarity to a real 

 fecundation than in Dudresnya, yet the nuclei of the two cells never 

 fuse. The sporogenous cell merely leaves its original abiding place 

 to take possession of the auxiliary cell, using it as a basis from which 

 to develop the spore fruit ; for the nuclei of the auxiliary cell either 

 disappear, or, if they persist, take no part in spore-fruit formation. 

 The nuclei of all the cells of the spore fruit are descendants of the 

 sporogenous nuclei, and are therefore sporophytic nuclei, while those 

 of the auxiliary cells are gametophytic. The process occurring in 



1 In addition to the authors mentioned above see also Philips, '95, '96, '97, '98. Osterhout, '96. 

 Hassenkamp, '02. 



8 See Oltmanns, '98, Taf. vn. Figs. n-ao. 



