- 173 — 



upon the different stages of age and partly upon the depth and the move- 

 ment of the water. 



Three forms of this species are easily distinguishable (at all events 

 the extreme forms): the main form or typical form, another form occur- 

 ring in exposed situations and a third form occurring in more sheltered 

 places. 



The specimens, which 1 have referred to the main form, are consi- 

 derably varying. The stipe is 5—113 cm. long, the lamina 10— 200 cm. 

 long and 10—50 cm. broad. As a rule the base of the lamina of the 

 narrower specimens is cuneate, while the lamina of the broader plants 

 has a cordate base. 



The lamina consists of a thinner, more or less broad and usually 

 strongly waved marginal area, and a thicker, more or less rugous and 

 bullate middle area. Alternating with more or less deep depressions the 

 bullations form a row on each side of the lamina between the marginal 

 area and the finely wrinkled or sometimes almost smooth central jjortion 

 of the frond. The sorus occurs in the middle of the upper part of the 

 lamina, and usually forms one longitudinal row up to 10 cm. broad, but 

 sometimes 1 have found it consisting of two, narrow, longitudinal rows 

 or forming patches of irregular shape. The consistence of the lamina is 

 highly varying ; specimens, the lamina of which have a thick and coriaceous 

 middle area, are to be found in the upper sublitoral region on a some- 

 what exposed coast. Specimens with long and narrow lamina, the marginal 

 area of which is pro[)ortionally narrow, and the middle area thick and 

 leathery, form the transition to the f. linearis. In deep water, especially 

 in sheltered places, the middle area of the lamina becomes proportion- 

 ally thin and almost smooth; such specimens are nearly connected with 

 the f. latifolia. I suppose the change of lamina takes place during the 

 wintermonths, as specimens bearing a rest of the old lamina were met 

 with in April — May and June. Fructiferous specimens have been collected 

 in May, July, and January. 



The main form occurs in the above mentioned Laminaria zone, espe- 

 cially in its upper part. 



The f. oblonga Stromf. 1. c. is to be referred to the main form. 



f. linearis J. Ag., Kjellm. Arct. Alg. p. 229, Handbok p. 25; Stromf. 

 Algveg. p. 42; Borgesen Faer. Alg. p. 451, fig. 85. 



Some of the Icelandic specimens, I have seen, agree very well with 

 the Faeroese plants described and figured by Borgesen (1. c). but other, 

 having much longer stipes, are somewhat differeut. It occurs on exposed 

 coasts at low-water mark. 1 have only seldom met with typical specimens 

 of this form, but on further searching it will surely prove to be more 



Botanisk Tidsskrift. 25. Bind. 12 



