1917] DUNN—DUMONTIA 457 



t 



f 



Nemastoma the transitional form between the Nemalionales and 

 the Cryptonemiales. The auxiliary cells of Nemastoma do not 

 occur in special branches, but are modified cells of the cortical 

 hyphae. Thus in Nemastoma there are no auxiliary cell branches 

 which can be considered as homologous with the carpogonial 

 branches. But there is also the evidence which has been presented 

 1 that the auxiliary cell branches in some forms as in Dumontia are 



I not vegetative hyphae which have by chance become highly special- 



ized in the same manner as the carpogonial branches. Thus the 

 sporogenous filaments, structures which are peculiar to this one 

 order, the Cryptonemiales, have probably been developed along 

 two independent lines. 



The female reproductive organs of the other red algae are 

 relatively simple when compared with those of the Cryptonemiales. 

 It is not surprising that the history of the nuclei in the sporogenous 

 filaments and auxiliary cells of the members of this order was an 

 especially puzzling problem to the earlier students. It has been 



i 



stated in the introduction to this paper that the origin of the nucleus 

 functioning in the auxiliary cells at the time of the formation of the 

 carpospores proved to be a stumbling block to most of these stu- 

 dents. The results of the work of Schmitz on certain genera of the 

 Cryptonemiales, including Dudresnaya, Dumontia, and Gloeosiphonia, 

 were conflicting in regard to the occurrence of a fusion between the 

 sporogenous and auxiliary ceil nuclei. Oltmanns' (9) investiga- 

 tion established practically beyond doubt the two following facts: 

 the sporogenous and auxiliary cell nuclei in Dudresnaya and 

 Gloeosiphonia do not fuse, and the nuclei in the carpospores are 

 descended from the sporogenous nucleus and not from the original 

 auxiliary cell nucleus. 



No member of the Cryptonemiales has been carefully inves- 

 tigated since 1898 in regard to the occurrence of a nuclear fusion 

 in the auxiliary cell. A considerable amount of excellent work, 

 however, has been done on other red algae during the last 17 years. 

 The fusion nucleus or one of its daughters, in many genera, has 

 been traced from the carpogonium into the auxiliary cell. The 

 fusion nucleus in all these forms appears to take charge of the cyto- 

 plasm in the auxiliary cell and becomes the ancestor of the nuclei 



