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edentatus, var. evanescens and var. linearis. The specimens referred to 

 var. edentata resemble well enough F. edentatus De la Pyl., but as the 

 var. evanescens is taken as before limited, it also includes forms, thai 

 ought not to be referred to it, and either belong to the main form, to 

 the narrower forms or to the dwarf forms of F. inflatus. The most of the 

 Greenlandic material is referred to var. evanescens, but Rosenvinge points 

 clearly out that it is closely connected with var. edentata and on the 

 other side also with var. linearis, in the Fferoese material Borgesen 

 (Faer. Alg. p. 465) found three forms of F. inflatus : f. edentata (= F. eden- 

 tatus De la Pyl.), f. disticha (F. distichus J. Ag.) and f. linearis. 



Kjelhnan divides later (Handbok 1. c.) F. inflatus into two varieties : 

 a finmarkicus and ^ nordlandicus, of which the former besides being 

 shining are characterized by wide axils, scattered and irregularly situated 

 conceptacles, while the latter is not shining and has narrow axils and 

 small and dense conceptacles. I have tried, but in vain , to group the 

 Icelandic specimens by these characters. ThQ density of the conceptacles 

 I have found varying in the same individual, as 1 have found plants both 

 having receptacles with large, scattered and prominent conceptacles, and 

 other receptacles, with small and dense conceptacles, which, 1 think, were 

 not fully developed. In my material the fully developed receptacles always 

 have large and prominent conceptacles, and I think the conceptacles, in 

 younger state of development, are smaller and more densily situated. The 

 shape of the receptacle is also not to be depended upon as a determining 

 character, as in the same individual we can meet with short, broad, un- 

 divided receptacles and long, linear, bifide ones, or also multifide recep- 

 tacles. The characters I have found most practicable are essentially the 

 size and the consistency of the thallus. 



1 take the species here, as it is limited by Rosenvinge (1. c), and 

 divide it into four forms, giving only name to the typical forms, which 

 are easily recognizable. It is useless to give name to the many transi- 

 torial forms; most of them could not be so plainly described as to be 

 recognizable and the description would, for the most part, be fiulividual. 



As I think the variation of this species is due to environmental in- 

 fluences, I define them as forms, but not as subspecies (Stromfelt) or as 

 varieties (Rosenvinge). 



f. tijpica. 



F. furcatus Kleen p. pte., F. evanescens auct. p. pte. ; 



F. edentatus De la Pyl. 



Fig. Fl. Dan. Tab. 1127; Borgesen Faer. Alg. fig. 90 and 01. 



The Icelandic specimens attain a length of 1 m. The breadth of 

 the frond is variable, it is usually 1 — 2 cm., but in the broader forms it 



