752 



and the slalk is, as pointed out by Will e (85, p. 9 — 10), very extensible, 

 in contrast to Laminaria hyperborea whicli has a very stiff stalk. 

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

 flexibility, whicli is also mentioned by Wille (p. 6). The plant is 

 moreover lirmly 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 

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

 form stenopijUa which is represented liere, but wliere the association is 

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

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

 lata, Cladophora riipesfris, Phijmatolithon polijmorpluim, etc. and on 

 the Laminarice themselves, some smaller epiphytes wliich grow on 

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

 thallus. Among the latter Ectocarpiis fasciciilatus, E. tomentosiis and 

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

 of the parasitical Ectocarpiis iomentosoides is invariably found (com- 

 pare 8, p. 415). 



Tlie Laminaria c/zg'z7rt/<7- association grows at about the same 

 height as the //zma/7//?a/za-association 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 sacc/zarz/za- association 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 wdiich I think might be refer- 

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

 This form w^as 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 Pogotrichnm filiforme , wdiich made the alga resemble an 

 ostrich feather wdien floating. 



The Alar ia- Association. 



This association generally grows uppermost in the sublittoral re- 

 gion directly below the Himanthalia-fonnaiion, as pointed out by Ha n- 

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

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

 exposed places, in clefts, or on sloping rocks that are constantly 



