tion, so far as I have been able to judge, always taking place 

 successively. In some species, and especially those provided with 

 superficial conceptacles, it appears, however, that the walls of the 

 tetrasporic sporangia are founded in a more quickly succession. 

 In others, on the contrary, and especially in species with immersed 

 conceptacles, the partition takes place in a more slow succession, 

 and the middle wall often appears to be fully or nearly fully 

 developed before the two other walls are founded. Thus it often 

 looks, as if the sporangia were only bisporic, sometimes with a 

 well developed wall, sometimes even looking fully developed, but 

 others in the same conceptacle or in other ones of the same spe- 

 cimen showing more or less indistinct partition of the one or both 

 cells; or one or both other interwalls partly so far founded partly 

 more developed, and the partition at first issuing only from the 

 one side. 1 ) Once I have seen the middle transverse wall later 

 developed than the two other walls. And in the same group of 

 species I also have seen overgrown sporangia only two-parted, 

 probably not fully developed before they, together with the con- 

 ceptacle, grew down into the frond. It is in this connection to 

 be remarked, that I, on the other hand, have not seen anj'thing 

 which with probability seems to suggest, that a species produces 

 both bisporic and tetrasporic sporangia. If perhaps it may now 

 and then occur, that a species provided with the one kind of 

 sporangia also bears fully developed sporangia of the other kind, 

 this must most probably be considered only an abnormal develop- 

 ment. So also in regard to the three-parted and irregularly three- 

 or four-parted sporangia which occasionally may be met with, 

 though in all seldom and, so far as I have seen, only in species 

 of the section Innatce. 



Thus the only distinction between the named genera consists 

 in a difference as to the vegetative part of the plant. In this re- 

 spect I refer to Sol ms-Lau bach 1. c, who has shown almost 

 fully transitions between both. 2 ) Moreover, Rosen vinge mentions 



l ) Cp. under L. orbiculatum, L. corallmdes and other species. 

 -i Mentioning Lithoihamnion Solrns-Laubach remarks 1. c. p. 26: „Bei- 

 consequenter Amvendung des unterscheidenden Merkmals warden freilich 



