130 



Tromsø Museums Aarshefter 14. 1891. 



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The vertical part is repeatedly branched with always 

 distinct main axis, though most often with branehes of only 

 two orders. The main axis is near the basis 27 — 33 [x 

 thick, attennated or sometimes of the same thiekness a little 

 upwards. It is polysiphonous almost after its whole length, 

 the segments are divided into 2 — 8 cells seen from the sur- 

 face, 2 times shorter to l 1 /* time longer than thick, cylin- 

 drical or cylindric-ellipsoidical with thick walls, always 

 thicker than in northern specimens of I. sphærophora. 



The branehes of the first order are in general elonga- 

 ted, sometimes simple or nearly simple, very numerous, most 

 often irregularly issuing withont any order, seldom opposi- 

 te, but sometimes subsecund, patent or commonly issuing in 

 a right or nearly right angle, often curved or bent in zig- 

 zag and more or less attennated towards the summit. The 

 branehes of a higher order are mostly shorter, irregularly 

 scattered or subsecund. Sometimes the branehes are mono- 

 siphonous, sometimes and most often partly polysiphonous, 

 16—20 \k thick with the segments (or cells) V a — 2 times 

 the diameter in length, more often cylradrical than those 

 in the main axis. The upper cells of the bianches are not 

 seldom nearly hyaline with the length until 5 times the 

 diameter. 



The chromatophores are, as far as may be seen in dri- 

 ed specimens, disk-shaped like those in i. sphærophora but 

 numerous and densely packed except in the upper part of 

 the branehes. 



As to the development of the branehes and sporangia 

 the species corresponds with I. sphærophora, but it is sub- 

 ject to much more variations than the latter. After a di- 

 vision of a cell iu the last named species by a longitudinal 

 wall into two cells, or more commonly by two longitudinal 

 walls into three cells, both the outer ones give rise to spo- 

 rangia, or to a sporangium and a brancli. In L rupincola, 



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