(10 ) 



the water remains brackish. Perennial. Summer and winter. Evei-ywhere common. — 

 /3. In salt marshes occasionally flooded. Not uncommon. 



Geogr. Dist. — Atlantic shores of Europe and North America ; Mediterranean, Baltic, 

 Icy Sea, White Sea ; Iceland ; Greenland ; Nova Zembla ; Spitzbergen ; California ; Sitka 

 and Sachalin ; Siberia ; at Ochotsk and Kamtschatka ; Canary Isles. 



Description. — Root, a hard, spreading disc. Fronds from one to two 

 feet or more in length, and nearly half an inch in breadth, with a strong 

 percm-rent midrib, occupying nearly one-fourth of its breadth, repeatedly 

 and regularly dichotomous, frequently spirally twisted, the margin flat 

 and very entire, the axils and apices broad and rounded. Air-vessels 

 large, generally in single pairs, or forming a continuous line on each side 

 of the midrib. Receptacles large, terminal, roundish ovate, oblong or 

 lanceolate, containing within the periphery numerous spherical " con- 

 ceptacles," which communicate with the surface by a minute pore, 

 containing, attached to their inner surface, obovate spores or antheridia 

 in different plants. Structure : the greater part of the frond is composed 

 of delicate longitudinal anastomosing fibres closely packed together, and 

 slightly coloured, the periphery very thin, consisting of vertical closely 

 packed filaments, highly coloured, forming a kind of coriaceous epidermis 

 much denser than the interior. Substance, when dry, very tough and 

 leathery. Colour, when fresh, a fine deep olive green, when dry nearly 

 black. 



This is one of the most common as well as the most generally dis- 

 tributed species of the genus, having been found not only on all the 

 northern shores of the Atlantic, but even on those of the Pacific, gi'owing 

 scarcer, however, as we proceed southwards, and in the southern part 

 of the temperate zone probably disappears. In the northern Atlantic, 

 however, it extends to a very high latitude : we have specimens from 

 Bafiin s Bay, collected in 73°, and it is said to be equally abundant along 

 the northern shores of Siberia as far as the East Cape. 



The variety ^. Balticus is a most singular one, and such that no 

 one would ever suppose, at first sight, that it had even the most 

 distant affinity with the present species. It is an inhabitant of salt 

 marshes, but does not generally grow, as far as our observation goes, in 

 the water, but mostly in damp hollows, even among the thick grassy 

 herbage, and round the margins of the pools. It is curious, however, to 

 observe that although the greater number of the patches grow out of 

 the watei", yet of those that grow on the margin of the pools, those 

 adjacent to the water are the most luxuriant ; and we have a specimen 

 just now befoi-e us, gathered near Fort George, on the shores of the' 

 Moray Frith, from the margin of a shallow pool, on the surface of 

 which the plants forming the outer margin of the patch were partially 



