— 367 — 



of Acrosiphonia lanosa (Roth) J. Ag. according to Kjellman's description 

 (Acrosiphonia p. 100), but as they are sterile, and the vegetative branches 

 moreover not fully developed, I think they are, at all events provisionally, 

 to be regarded as indeterminable. My plants were gathered in the first 

 half of April and contained only a single nucleus in each cell. 



SW. I cel. Reykjavik. 



Acrosiphonia 1 ) albescens Kjellm. Acrosiphonia p. 55, Tab. IV, fig. '21, 

 Börgesen Fær. alg. p. 507, fig. 103; Spongomorpha arcta Strömf. Algveg. 

 p. 54, p. pte. 



This species is exceedingly common along the coasts of Iceland, 

 both in exposed and rather sheltered situations ; it is usually very gregarious 

 and forms widely expanded strata on stones and rocks in the litoral 

 region. My specimens are 2 — 13 cm. high, the main branches are 70 — 

 100'« thick above, and the sporangia occur singly or two or three or 

 more, up to 30, in a continuous row. My plants agree fully with Kjellman's 

 description, except the occurrence of more than three sporangia in a row 

 and the considerably larger height. Fructiferous specimens have been 

 gathered in April— October with richly occurring spinous branches and 

 hooked branches. 



J ) To the genus Acrosiphonia I refer only species containing many nuclei in 

 each cell. Thus limited Acrosiphonia only includes the subgenus Melan- 

 arthrum Kjellm. (Kjellm. Acrosiphonia p. 50), and I suppose the species 

 belonging to the subgenus Isochrous Kjellm. (Kjellm. Acrosiphonia p. 82) 

 having, probably all, only one nucleus in each cell, are to be referred to 

 Spongomorpha, as proposed by Wille (Botaniska Notiser 1899, p. 281). The 

 subgenus Melanarthrum is by Kjellman (1. c.) divided into three sections: 

 Speirogonicœ characterized by „Cellulæ fertiles saltim ab initio sparsæ, soli- 

 tariæ binæ vel ternæ", Zoniogonicæ characterized by „Cellulæ fertiles jam 

 ab initio 10 — 30 vel plures seriatæ. series intercalares formantes" and Acro- 

 gonicæ characterized by „Cellulæ fertiles jam ab initio ad complures seriatæ 

 series terminales formantes". Judging from the Icelandic material of Acro- 

 siphonia I do not find this division into three sections justifiable. Many 

 of my specimens, especially of those referred to A. albescens Kjellm., have 

 the sporangia occurring either singly or two or three or up to ten, and 

 even up to 30 in a continuous row, but I have also frequently met with 

 specimens, which had not more than three sporangia in a continuous row, 

 My material seems thus fully to agree with the Færoese plants described 

 by Börgesen (Fær. alg. p. 506) and I think the sections Speirogonicæ and 

 Zoniogonicæ are to be united, as Börgesen points out (1. c). Whether the 

 section Acrogonicæ is to be maintained is also highly doubtful, as I have 

 met with specimens having both terminal and intercalar sporangia occurring 

 singly or up to 5 in a continuous row. 



24* 



