ALG«. 287 



the bed of the lower part of the Tweed during the summer, and are 

 well known to our fishermen under the name of S>la&e, for, by 

 clogging his nets, they offer a serious obstacle to his work. The 

 Confervse so common in bums in the heat of summer are called 

 ^tttruMooti. 



The fresh-water Algee have a few species (Chroolepi, Nostoc, Pal- 

 mellse, &c.) which leave the water to make acquaintance with the 

 Fungi ; and some marine species (Ralfsia and Cruoria) come almost 

 in contact with the Lichens. Some, to connect the fresh-water and 

 marine kinds, occupy brackish waters. Of this intermediate class 

 are the Conferva tortuosa which covers the tide-bathed margins of 

 the Tweed in spring ; and the Enteromorphie which extend from the 

 sea to beyond the reach of salt water, and as far as the influence of 

 the tide is felt in the Tweed and Whiteadder. The Fucus vesicu- 

 losus accompanies them into water that is only slightly tainted, for 

 it is found at the mouth of the Whiteadder, and in the Tweed as far 

 as the Union-Bridge ; but the character of the plant is altered by 

 the change, for the river plants are thinner, darker-coloured, and less 

 loaded with vesicles than the marine, and the ends of the divisions, 

 in the spring season, are much enlarged and swollen with air *. The 

 Ectocarpus littoralis meets this Fucus so soon as the water of the 

 river becomes salted, at all tides ; and as we near the mouth, Fucus 

 canaliculatus, serratus, and nodosus appear almost coetaneously, with 

 some marine confervse. 



There are zones of vegetation on our shores marked by peculiar 

 species, but the limits are rather loosely defined, and the species fre- 

 quently intermingle. The Fucoidese occupy, with their blackness, 

 all the space between low and high water marks, living an amphi- 

 bious sort of life, alternately exposed to the atmosphere, and covered 

 by the tide. The proper Fuci form the outer band of the zone, 

 while the Halidrys and Himanthalia appear principally on its inner 

 or sea margin ; and the greater portion of sea-weeds intermixed grow 

 in the intermediate space, giving variety to the shore by their green 

 and olive and purple fronds. The Laminariese occupy a lower 

 region, for they are strictly aquatic, and choose therefore a station 

 not liable to be left dry at the reflux of the tide. You may see them, 

 within the ledge of rocks that bounds our sea at its lowest ebb, 

 floating on the heaving ocean, their broad dark fronds rising in the 

 furrow of the wave and again dipping beneath on its swell, in a sort 

 of luxurious motion that you almost envy. The day is sunny and 

 tempting, and you approach nearer, admiring that singularly beau- 

 tiful vegetation which crowds every crystal pool in the rocks you 

 walk over ; exceeding in beauty the plants of the earth f . Often 



* Compare with Fleming's observations in Ann. and Mag. N. Hist. Ser. 2. 

 ii. p. 67- See also Professor Edward Forbes on the zones occupied by 

 Sea-weeds and marine Invertebrata, in Ann. and Mag. N. Hist. Ser. 2. vii. 

 p. 232. 



t Our sea-side visitors in summer — if pretty and young — are sure to be 

 admirers of Ptilota pluraosa and Plocamium coccineum ; and they preserve 



