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of the axis, the one produced from the cells of the axis, the other from 

 the cells of a lateral branch entirely resembling those of G. gracilis (fig. 19). 

 The sporangia occur few or many (up to 10 or more) in terminal rows 

 and their opening is situated near the upper end. 



Regarding the branching, this form sometimes habitually resembles 

 Gladophora hirta Kütz., especially specimens I met with at Reykjavik in 

 March consisting of a short main axis and proportionally long branches, 

 which evidently had endured the winter; the branches were furnished 

 with many, short and young branchlets on account of which the plants 

 superficially resembled G. hirta, but as the branchlets during the summer 

 months become repeatedly branched and grow long the summer-plants 

 are to be referred to C. sericea. I have also in summer occasionally met 

 with plants somewhat reminding of G. hirta, viz. plants in which the 

 emptied rows of sporangia had fallen away. In this way the branchlets 

 become shorter and the contrast between long and short ramifications 

 more distinct. 



Fructiferous specimens have been gathered in April, July and Sep- 

 tember. 



NW. I cel. Kolbeinsâ. 



SW. I cel. Stykkishölmur , Ölafsvi'k , Öndveröarnes , Einarslön, Rey- 

 kjavik ; Njarövik (G. O.). 



S. I c el. Vestmannaeyjar. 



Cladophora giaucescens (Griff.) Harv. Phyc. Brit. Tab. 1 96. Le Jol. 

 Alg. mar. d. Gherb. Exsicc. 66. 



To this species I have referred some plants collected by Ostenfeld at 

 Reykjavik in the litoral region, as they seem to agree with the figure 

 given by Harvey (1. c.) and Le Jol. Exsicc. Nr. 66. 



SW. I cel. Reykjavik (CO.). 



Cladophora gracilis Kütz., Kjellm. in Wittr. etNordst. Exsicc. Nr. 1040. 



As far as I can see from the dried specimen in the named Exsicc. 

 Nr. 1040, my specimens seem to agree with the plants distributed by 

 Kjellman under the name Gladophora gracilis Kütz., and they differ from 

 the figures of G. gracilis given by Harvey (Phyc. Brit. Tab. 18) and 

 Areschoug (Phyc. scand. Tab. II, B, fig. 1—2). Most of my plants have 

 been gathered in pools in the lower litoral region and amongst Fucaceæ 

 in the middle part of the litoral region, and only one gathering is from 

 a depth of 3 — 4 fathoms. The length of some of my specimens is con- 

 siderable, more than 15 cm., and the thickness of the main branches is 

 varying from 80 — 140 /j. The branching of the apex is dichotomous, or 

 the branchlets are more or less secund and sometimes verticillate (fig. 18). 

 The cells in the middle part of the frond are up to 13 times longer than 



