— 368 — 



Acrosiphonia incurva Kjellm., Acrosiphonia p. 61. 



This species is also common in rather sheltered situations, and occurs 

 for the most part in litoral pools, I have however sometimes met with 

 it forming large strata on stones or rocks in the lower litoral region, 

 being left dry at the ebb. My specimens are 2 — 8 cm. high, and the 

 main branches are 130 — 170/i thick above. Some specimens, which I 

 gathered at Reykjavik in April, had some few spinous branches but as 

 they in other respects agreed with the description of A. incurva Kjellm., I 

 have referred them to it. Fructiferous specimens have been gathered in 

 April — June. My plants seem to agree very well with Kjellman's description 

 except the occurrence of spinous branches. It is possible, as Kjellman 

 (1. c. p. 62) points out, that A. incurva is a spring form. The plants 

 described by Kjellman were gathered by Foslie in Finmarken in May, the 

 Færoese specimens (Börgesen Fær. alg. p. 510) were fructiferous also in 

 May and the Icelandic plants have been collected in April— June. A. incurva 

 Kjellm. is essentially separated from A. albescens by thicker main branches, 

 by the want of spinous branches and on the whole by looser growth, 

 but as I have met with specimens of A. incurva with spinous branches, 

 I think it probable that these two species will turn out to be identic. 



I have never in my material of Acrosiphonia met with specimens 

 that exclusively or even in the greatest part of the cells have had a 

 chromatophore of the same structure as described and figured by Kjellman 

 in Acrosiphonia centralis (Lyngb.) Kjellm. (Kjellm. 1. c. p. 72, Tab. IV, 

 fig. 15, 19 — 20), but I have sometimes met with plants of A. incurva, 

 which, especially in longer cells, had somewhat resembling chromatophores 

 while the meshes of the chromatophores in the shorter cells were much 

 smaller. On the whole, I think that the largeness of the meshes of a 

 reticular chromatophore is not to be relied upon as a specifically distinctive 

 character (cfr. also Urospora p. 361), and consequently it is questionable 

 whether A. centralis Kjellm. is specifically distinct from A. incurva Kjellm. 



Acrosiphonia hystrix (Strömf.). 



f. typica, Spongomorpha hystrix Strömf. Algveg. p. 54, Cladophora 

 diffusa Strömf. Algveg. p. 55, p. pte. (e specim.); Cladophora (Spongomorpha) 

 arcta y hystrix Rosenv. Grl. Havalg. p. 907. 



The most typical specimens agree precisely with Strömfelt's description 

 (I.e.) and his original specimens from Iceland. My plants are 9— 15cm. 

 high. The thickness of the main branches varies from (240— )300 — 400^. 

 The branches of the last order are for the most part secund and attain 

 almost the same thickness as the main branches; they are often thickest 

 in the middle and measure at the base about 260^, in the middle about 

 300—350 fx and at the apex about 250 ju. Old branches in which vege- 



