the Marine Algce of the Firth of Forth. 



45" 



From these and other figures the general conclusions 

 seem to be justified that there is almost invariably an 

 increase in average size as we advance seawards, when the 

 same species is examined at a corresponding level within 

 the tidal zone. 



If specimens belonging to the same species be examined 

 at different levels within that zone or in deeper water, it is 

 possible, in many cases, from this point of view as well as 

 from that of mere numbers, to recognise a level at which 

 the plants grow to greater advantage than in other (higher 

 or lower) positions. Thus, although in parts at or near 

 high-water Laminarice flourish, they are invariably of 

 diminutive size, e.g., L. cloustoni and L. flcxicmdis may 

 only attain the length of 18 to 24 inches, while in 

 the true Laminarian zone they are not unfrequently 

 got up to 8 or 10 feet. Phyllophora traillii is of finest 

 growth at or below the limits of lowest spring tides ; but 

 in dark crevices of rock, even though somewhat muddy, it 



