32 



CARL SKOTTSBERG, MARINE ALG^ 1. PHiEOPHYCEJE. 



not uncommon in the Chordariacese. The horizontal thallus is very firm and has 

 marginal growth; the oldest stumps of erect fronds are found in the centre, every 

 year a new zone being added. The old surface is rough from remains of old upright 

 fronds while the fresh marginal parts are smooth and of a lighter colour. There is 

 nothing like this in Scytothamnus. The structure of the crust is monosiphonous, see 

 fig. 13 d. The erect fronds are solid; there is, even in the youngest stages, no 

 apical cell nor one central filament, but a bundle of longitudinal filaments (fig. 13 e). 

 Sections of old fronds show numerous hyphse, most of them running longitudinally, 



Fig. 13. a Mesogloea falklandica, nat. size; b Chordaria linearia, part of long. section, X 180; C— g Stereo- 

 cladon rugulosus; C horizontal thallus on Mytihis, with stumps of erect fronds, nat. size; å section through 

 margin of horizontal thallus, X 180; e long. section of growing apex, X 300; f cross section of erect fond, 



X 180; g id. with ripe sporangia, X 180. 



malung the medulla very solid and unlike the structure of Scytothamnus. The mode 

 of growth also separates Stereocladon from Scytothamnus or Dictyosiphori, and it cannot 

 be placed in the same order with them. I think that Hariot was right in removing 

 it to the Chordariacea?, even if he does not tell us why he did so; the structure, 

 on the whole, seems to defend its new position. The assimilators, I admit, are 

 unlike the common type in that order, but it is difficult to find a better po- 

 sition for it. 



Distribution: Subantarct. Amer., Falkl., S. Orkn. Isl. 



