OLIVE COLORED ALGyS. 77 



Genus. — HALIDR YS* Lyngb. 



Halidrys osmundacea, Harv. 



This elegant plant forms a prominent feature in 

 the marine flora of southern California. It grows in 

 abundance at San Diego, below tide, and in the 

 sluice-ways cut in the rocks by the water. It is 

 thrown on shore at all seasons. It is also abundant 

 at Santa Barbara, but absent at Santa Cruz. At all 

 events, that acute observer. Dr. Anderson, does not 

 report it as present. It grows from a discoid hold- 

 fast, a roundish flattened stem, as thick as a goose 

 quill. Flattening more and more upwards, the stem 

 divides or branches, and puts out from its edges, 

 winglets, or alternate leaves, from one to two inches 

 long, which, like the flattened stem, are thick and 

 midribed. Near the middle of the stem these 

 cease, and the stem becomes rounded again and 

 alternately branched, the branches also branching 

 alternately in nearly the same plane. The secondary 

 cylindrical branchlets form the air vessels of the 

 plant, by being much swollen and hollow, and 

 constricted at regular intervals, giving them an ap- 

 pearance not unlike a string of coarse black beads. 



* Ha]idiys=Sea Oak. 



