— 34G — 



walls from 1,5 — 6^. The cells of the lower part of the frond are, in 

 transverse section, 6 — 9/^ high and i — 1 p. broad, but those of the upper 

 part of the frond are usually somewhat lower; both the frond and the 

 walls are thinner upwards, but the relation between the inner and the 

 outer walls is usually the same as below although specimens having inner 

 and outer walls of about the same thickness above also occur. The 

 diameter of the cells, seen from the surface, varies from 4—10^/, and 

 the cells are usually rounded or indistinctly five-sided with rounded 

 angles. The transverse section of the frond of my plants resembles in 

 the most cases entirely the figure given by Rosenvinge (1. c. p. 958, fig. 54), 

 showing, as a rule, a heteregenous inner v^all, but species with a homo- 

 genous inner wall, as figured by Ahlner (Enieromorpha fig. 7 h), also 

 occur. There is no distinct limit to be drawn between this form and 

 f. genuina, and transitory forms are almost as common as the typical 

 forms , in which respect my material resembles the Greenlandic and 

 Faeroese material. 



The typical f. micrococca has, as I have said before, an inner wall 

 much thicker than the outer, but specimens having the inner and the 

 outer walls equally thick or even the outer wall thickest also occur in 

 my material, and 1 have occasionally met with specimens showing the 

 different stages of this variation of the wall-thickness occurring in the same 

 individual. The same variation of the thickness of the walls of this 

 form has already been observed in tlie Fa^roese specimens (Borgesen 1. c. 

 p. 490). 



Stromfelt (1. c.) does not mention this form from Iceland, but 1 have 

 in his collections from Iceland, found a specimen, collected at IsafjorSur, 

 which undoubtedly belongs to f. micrococca (cfr. under f. genuina). 



The f. micrococca grows on stones and rocks at or above high-water 

 mark. Fructiferous specimens have been collected in June — October. 



f. compressa (L.) Rosenv. 1. c. p. 958. 



Enteromorpha compressa f. typica and Enteromorpha complanata 

 f. subsimplex Stromf. Algveg. p. 53. 



The specimens I have referred to this form are 2—20 cm. high, 

 0,5 — 2 mm. broad and 12 — 30 ^ thick. The inner and the outer wall 

 are usually of the same thickness, but specimens with compressed frond 

 and a somewhat thickened inner wall, also occur. In the transverse section 

 the cells are as high as broad or twice as high as broad. Seen from 

 the surface the cells are four- or five-sided or rounded and in the lower 

 part of the frond sometimes arranged in rows. The diameter of the cehs 

 seen from the surface, is highly varying; in the same individual 1 have 

 seen cells having a diameter of 4 — 6/^, and other cells, in the middle of 



