44 



iterated division of the lowest living cell, and the new part of 

 the rhizoid is distinctly marked from the old one by a sheath 

 formed by the remaining walls of a dead cell. In the same 

 way the uppermost branches, when injured, are renewed by an 

 iterated division of the uppermost living cell, and the lower 

 end of the young branch is enclosed in a sheath of a dead cell. 

 Sometimes more than one sheath is to be seen in the young 

 branch showing that the branch has been repeatedly renewed. The 

 young branches produced in this manner are usually consider- 

 ably narrower than the older part of the branch and often highly 

 resemble flagelliform branches ; consequently the occurrence 

 of flagelliform branches is of a doubtful value as a specifically 

 distinctive character. Such renewed growth of the branches is 

 certainly sometimes produced in the manner, that the uppermost 

 part of a branch above some emptied sporangia is thrown off, 

 and the cell next to the emptied sporangia forms a new apex 

 by iterated division, but in most cases it is produced in the 

 way, that the uppermost part of the branches injured by the 

 air during the ebb dies off and grows out again as milder 

 environmental influences play upon it. This is concluded from 

 the frequent occurrence of renewed growth in the branches of 

 young, sterile specimens. Such renewed growth of branches 

 and rhizoids is before described in Acrosiphonia flabelliformis 

 (Jonsson Icel. Alg. p. 371, fig. 16 a, fig. 17 b-e). 



Regarding the structure of the chromatophore the Green- 

 landic specimens fully agree with the Icelandic plants (Jonsson 

 icel. Alg. p. 368), and the largeness of the meshes of the chro- 

 matophore is, I think, not to be relied upon as a specifically 

 distinctive character. As A. incurva Kjellm. differs from A. 

 centralis (Lyngb.) Kjellm., only by the largeness of the meshes 

 of the chromatophore, I think that on further investigation they 

 will turn out to be identic, and in that case the older name, 

 A. centralis (Lyngb.) Kjellm., should be used. 



Some rather peculiar specimens have been collected by 



