— 112 — 



the internodes was common (up til 30). I found tetraspores in the 

 specimen from Stykkisholmur. 



Ceram. arborescens J. Agardh; Pl. II; fig. 6. 



A specimen collected at Reykjavik 5 /e 1886 by Kolderup Ro- 

 senvinge is a beautifully developed C. arborescens (bearing tetraspores). 



Specimens collected in Hrisey (N. Iceland), 2 h 1898, by H. Jons- 

 son and in Lâtravik in Adalvik (N. W. Ic), 8 /? 1896, by Ostenfeld 

 are related to this species, but certain conclusions not possible. 



Ceram. atlanticum sp. nov.; Pl. I, fig. 2 a; Pl. II; figs. 7, 11 and 

 12; Fig. V, 2. 



Ramificatio dichotoma vel plus 

 minus irregularis; anguli ramorum 

 sæpe acuti. Rami secundarii fréquen- 

 tes sæpe secundati ut in forma secun- 

 data Ger. rubri. Cortex in partibus 

 superioribus confluens vel in zonis 

 breve spatium inter se distantibus 

 marginibus rectis instructis constat. 

 In partibus intermediis zonæ structura 

 ut in Cer. Rosenyingii gignuntur. In 

 partibus inferioribus cortex confluens. 

 Cellulæ in cortice externo diam. 2,5 — 

 7,3 x 3 fi. Cellulæ corticales réfrin- 

 gentes paucæ, in partibus inferioribus, 

 adsunt. Tetrasporangia verticillata 

 seriata. Pili fréquentes. Color vario 

 modo rubescit. In maribus apud oras 

 Færoenses (et Islandicas?). 



The ramification is dichotomous 

 or with development of main axes, 

 often with very acute branch-angles. 

 The apices forcipate. Secondary shoots 

 are common, sometimes placed uni- 

 laterally as in forma secundata of Cer. 

 rubrum. 



The bark is near the apices either 

 rubroid or developed in zones close 

 together with sharply confined mar- 

 gins. Below this part we find zones with growing upper and 

 lower margins as the case is in the group of C. Rosenvingii-arbor- 

 escens. At last totally confluent bark. Nowhere large interstices 

 between the zones; the zones when free always lie close together. 

 The cells in the outermost parts of the bark are small, 2,5 — 7,3 x 



2 



Fig. V. 



1. C. circinnatum; 2. C. atlanticum, zone 

 in the middlemost part. X 160. 



