752 



and the slalk is, as poinled out by Wil le (85, p.9 — 10), very exlensible, 

 in contrast lo Laminaria hijperhorea which has a very stiff stalk. 

 The stalk being often miich compressed at the top, adds to its 

 llexibility, which is also mentioned by Wille (p. 6). The plant is 

 moreover firmly fastened to the rock by vigorous haptera, and if 

 one tries to pull it up, generally only the stalk is broken, whilst the 

 haptera are left. On coasts where the rocks project vertically into the 

 sea, this association, however, is usually entirely absent, or a single 

 Laininarin digitata at most may now and then be found. It is the 

 form stenopijUa which is represented here, but where the association is 

 well developed, all transitional forms besides the main form are found. 

 As a subvegetation, we find Corallina, Gigartina, Polysiphonia nrceo- 

 lata, Cladophora riipestris, PhymatoUtlion polymorphum, elc. and on 

 the Laminariæ themselves, some smaller epiphytes which grow on 

 the stipes or sometimes also on the margin of the lobes of the 

 Ihallus. Among the latter Ectocarpiis fasciciilatiis, E. tomentosiis and 

 E. Hincksiæ are the most important. Early in spring a dense covering 

 of the parasitical Ectocarpiis tomentosoides is invariably found (com- 

 pare 8, p. 415). 



The Laminaria digitata -assocmlion grows at about the same 

 height as the Himanthalia-nssocintion which is usually absent where 

 the former is well developed. 



In connection with this I may say that I have also, though 

 but rarely, found a Laminaria saccharina- associalion growing a little 

 above and a little below the lowest water mark. On Sumbo Holm, 

 a little above the lowest water mark, I have found a vegetation of 

 L. saccharina represented by a form which I think might be refer- 

 red to f. linearis (see the illustration of this alga in my flora, 8, p. 453). 

 This form was smaller, the thallus narrow, thick, leathery and 

 very wrinkled, probably an adaption to its very exposed habitat. 

 On the lamina a great many epiphytes were often found, espe- 

 cially Pogotrichiim filiforme , wdiich made the alga resemble an 

 ostrich feather when floating. 



The Ålaria- Association. 

 This association generally grows uppermost in the sublittoral re- 

 gion directly below the /fm7a/j//?rt//a-formation, as pointed out bj^ Han- 

 steen. Thus it begins at about the lowest water mark at neap-lide; 

 at spring-tide, part of it, one foot or more, is laid bare. In very 

 exposed piaces, in clefts, or on sloping rocks that are constautly 



