the Marine AUjcc of the Firth of Forth. 453 



merribranifolia^ Delesseria alata, D. sinuosa, Melohesia lam- 

 minarice, Ft Hot a clegans, &c. 



With respect to this entire tidal belt, however, the 

 following circumstances are worthy of note : — 



(1) The range, though in all cases general, in a land- 

 ward direction, as contrasted with some deeper species as 

 already implied above, varies with regard to the three 

 great groups. Thus the Chlorophyceae extend furthest 

 inland, occurring, though in diminished size, well up to 

 the point to which tidal water passes, as in the case 

 of Enteromorpha, Ulothrix, &c. — while they at the same 

 time are found on shores bathed by the pure ocean 

 water. The Fucacece have the next greatest superficial 

 range. Himanthalia lorea is indeed confined to the 

 more seaward parts, and Fucus ceranoides is perhaps, after 

 it, the most limited in its range, but on the other hand, 

 F. nodosus and F. canaliculatus pass far up the estuary ; 

 the latter has not been observed beyond Queensferry, but 

 the former occurs as far as Grangemouth. F. serratus and F. 

 platijcarpus ascend as far as Alloa, and are of fairly large 

 size, and the latter can be traced still higher, notwithstand- 

 ing the mud which so greatly pollutes the river at this 

 part. Ectocarpus siUcidosus and E. littoralis also pass up 

 beyond Queensferry, but their growth has never been 

 observed to be so great as at more seaward localities. The 

 range of the species of Ulvacece and of Porphijrcc is also 

 of wide extent, though like the last they disappear before 

 the Fuci. Monostroma latissimum is more persistent than 

 the more delicate Ulva linza and V. lactuca. Species of 

 Ulothrix are of wider range, and pass gradually into 

 similar species belonging to fresh water. 



The species of Elachistea have a less wide range than 

 those of Fucus, although they are often found growing on 

 tlie latter. 



For those belts lying below the Enteromorpha area, a 

 general thinning off may, as in the latter, be observed as 

 the estuary is ascended, and as the water becomes less 

 deep, or as a sandy and shelly ground is replaced by mud. 

 Thus the Gigartina mammiUosa , which occupies a con- 

 siderable vertical area at Inchkeith, Fidra, and on the 

 adjoining coasts of the mainland, is not so extensive at 



