182 



THE OPAL SEA 



A popular 

 classifica- 

 tion of sea 

 weeds. 



Green dlgm. 



Blooms and 

 net weeds 



ture is higher than in the depths, and the yel- 

 low sunlight penetrates to the bottom. As the 

 shore shelves off into the sea the growths be- 

 come smaller and smaller, finally disappearing 

 entirely, so far as we know. In a very general 

 way the descent seaward is marked by the color 

 of the sea weeds ; and a popular classification of 

 them by color may be made, though it lacks 

 scientific accuracy. 



Along the shore, often in tide pools, rock 

 basins and marsh inlets are the numerous 

 groups and families of the class Chlorophycece 

 or green algcB. The color comes from the pres- 

 ence of chlorophyll in the cells, and the forms 

 are small and complicated. The bright-green 

 sea lettuce ( Ulva) , the iridescent white-banded 

 Peacock's Tail (Padina pavonia), the fan- 

 shaped cladophora {Cladopliora arcta), the 

 green laver (Porpliyra vulgaris), the sea bottle 

 (Valonia ventricosa) , with many moss-like, 

 netted, filamental, hairy, spiny, cactus-formed 

 plants, belong to this class. They are growths 

 that need sunlight and are not usually found 

 in deep water. 



Still another class of sea plants, Cyanopky- 

 cecB, need warm sunlight and grow near the sur- 

 face. In fact many of them grow on the top 

 of the water and are known to us as water 



