DUDRESNYA. 125 



Callithamnion , Glecosiphonia, Dasya and others is after all not so 

 extraordinary as it may at first appear, since the superior significance 

 of the nucleus in all constructive metabolism of the cell has been 

 thoroughly demonstrated. 



If the doctrine of Oltmanns be correct, and the facts seem to justify 

 his conclusion, we have in the sporogenous filaments of Dudresnya 

 and similar genera of the Rhodophycea a sporophyte, which, for the 

 purpose of nutrition, fuses with auxiliary cells, and, because of the 

 better nutrition, is capable of producing several spore fruits. The 

 auxiliary cells must, therefore, be regarded merely as special brood 

 cells, their fusion with the cells of the sporogenous filaments being 

 homologous with the fusion of vegetative cells. 



As regards the existence of an alternation of generations in the 

 Rhodophycece, there still remains the question upon which De Bary 

 laid some stress, namely, that in the Rhodophycea, as well as in the 

 Ascomycetes, there is no rounding up or separation of the egg as an 

 independent cell in the oogonium, such as occurs, for example, in 

 Coleochcete, in the Bryophyta and Pteridophyta. In the second 

 place the determination of the number of chromosomes in these gen- 

 erations and the point in the life-cycle at which the numerical reduc- 

 tion of the chromosomes takes place are factors, which, in the light of 

 important existing theories, must be taken into consideration. The 

 first of these questions may be of comparatively little importance, but 

 an alternation of generations in the Rhodophycece will probably not 

 be unqualifiedly accepted by some botanists until the question of the 

 chromosomes is definitely settled, or until the full significance of the 

 reduction is beyond question. 



A comparison of the process of fecundation and the immediate sub- 

 sequent development in certain Ascomycetes and Floridece reveals 

 several striking parallels, or, shall we say, homologies. In the first 

 place the female sexual organ in both groups is in all probability 

 homologous. The carpogonium, or oogonium, of the Floridece, with 

 its large receptive part, the trichogyne, may be compared directly with 

 the oogonium of the Discomycetes, e. g., Pyronema, and, perhaps, 

 with the carpogonium of the lichen Collema. The presence or 

 absence of a trichogyne is, moreover, of secondary importance, as this 

 organ is purely an adaptation to peculiar environmental conditions. 



All representatives of this type of sexual reproduction agree in that 

 the egg does not, by self-plasmolysis, separate itself as an individual 

 from the oogonium. Whether the gametes be uninucleate or multi- 

 nucleate is of little importance as viewed from a phylogenetic standpoint. 



