348 



especially, e. g. Ihe thickness of the thallus, and the number of the 



antherozoids and the carpospores in the antheridium and in the 



sporocarp respectively, as specific distinctions. How far this view, 



which appears to rae to be somewhat artificial, is the correct one, 



is rather doubtful, and no definite opinion of it can be formed until 



Hus's completed work is published. I therefore prefer at present, re- 



lying on my above-nientioned observations, to follow Rosen vinge's 



definition of species, all the more as I had finished the examination 



of my Po/yj/jj/ra-material before receiving Hus's paper. 



This species generally grows in the sublittoral zone and has 



been found down to a depth of 10 — 15 fathoms; it is also met 



with near extreme low-water mark especially in rock-pools, and 



grows both on open sea-shore and in sheltered piaces. Fructifying 



specimens were found in May, June and July. 



This species is very commonly distributed along the Færoes; as 

 inentioned by Simmons (1. c. p. 264) it was first reported from the 

 Færoes by J. Agardh, who, however, does not give the narae of the 

 discoverer, but it was probably L}'ngbye or Rostrup. 



5. P. umbilicalis (L.) J. Ag. Kjellm., N. I., p. 238 (190); Rosenv., 

 1. c. p. 830; Ulva umbilicalis Lyngb., Hydrophyt., p. 28. 



f. laciniata (Ag.) Le Jolis, Liste, p. 99. 



f. umbilicalis (L.) Kleen. 



f. linearis (Grev.) Le Jolis, 1. c. 



Formå laciniata is most commonly met with in somewhat 

 sheltered localities, occurring there in the littoral zone near high- 

 water mark, e. g. in the narrow part of Sundelaget, where examples, 

 some two feet long, are found spreading over stones and gravel. 

 Formå umbilicalis is extremely common and is met with abun- 

 dantly along all the coasts of the Færoes which are exposed to the 

 open sea, where it covers the rocks in small, low tufts resembling 

 crumbled paper; Wille calls the latter form ^ scopulorum 1 . It 

 somelimes extends to a considerable height above sea level. This 

 form always grows attached to rocks, but /'. laciniata mav some- 

 times be found epiphytic, e. g. on Fucus-species. Lyngbye found 

 f. linearis near Kvalbo on Sydero and some of the specimens in 

 my collections suggested this form. 



Fructifying specimens were found in May, June, July, October 

 and November. 



1 Wille, N.: Bidrag til Algernes physiologiske Anatomi, \i.'M. 



