178 OTTO VERNON DARBISHIKE. 



aggregations of cells represent portions of the thallus which are 

 chiefly assimilating. On the other hand, the form of the plants 

 resulting from the experimental germination of the tetraspores of 

 Actinococcus may be due to the very abnormal conditions under which 

 germination took place. 



In discussing the question a short time ago with Professor Reinke, 

 the latter suggested as a possibility, which ought not to be dismissed 

 prima facie, that Actinococcus might really be an asexual generation 

 of Phyll. Brodiaei, growing parasitically on the sexual generation. 

 Although this is not absolutely impossible, it is not very probable that 

 it represents the true state of affairs. I need only recall to mind the 

 fact that the contents of one antheridial cavity at least are destroyed 

 by the parasite entering the host. 



The foi^egoing paper was written for the purpose of definitely 

 settling the nature of the pseudo-nemathecia of Phyll Brodiaei (Turn.) 

 J. Ag., of the parasiticum quid of Lyngbye, of Actinococcus subcutaneus 

 (Lyngb.) K. Rosen v. and Act. roseus Ktz., all of which represent the 

 nemathecia of Actinococcus subcutaneus (Lyngb.) K. Rosenv. 



Other species of Phyllophora Grev. and of other closely related 

 Gigartinaceae and other sj)ecies of Actinococcus Ktz. and allied 

 genera, are about to be examined by the author. It is a remarkable 

 fact that the nemathecia of Phyll. Brodiaei have not yet been found, 

 although this species is as common as Phyll. membranifolia (G. and 

 W.) J. Ag., the nemathecia of which are frequently met with, even in 

 the Baltic. It is necessary that this point also should be elucidated. 



There are frequently found growing on specimens of Phyll Brodiaei 

 in the Baltic, and more rarely in other seas, certain structures, which 

 have been called ' Traubenkorper ' (1, p. 9). Tetraspores, antheridia 

 and procarpia are found on these, but they never apparently attain to 

 maturity. Schmitz also mentions these peculiar bodies, referring them 

 provisionally as a new species to bhe genus Actinococcus Ktz. (5, p. 380). 

 Kolderup Rosenvinge has described a new species of Ceratocolax, -which 

 apparently embraces the two organisms just mentioned, and to which 

 he has given the name of Ceratocolax Hartzii K. Rosenv. (4, p. 34). 



The following is a brief description of the genus Actinococcus Ktz. 

 and species Actinococcus subcutaneus. It is my intention to give a 

 complete list of synonyms, literature and exsiccata in a later paper ; as 

 also a discussion of the systematic position of this plant. 



