OLIVE COLORED ALG^E. 75 



minute dark dots. The leaves vary greatly in length 

 and breadth and even in shape, being from one to 

 three inches long, and from one-eighth to one-third 

 of an inch wide. The air vessels which distinguish 

 the genus are numerous little globes, one-eighth of an 

 inch or more in diameter, set upon little stalks half an 

 inch long, which grow from the axils of the leaves. 

 Sometimes from the appearance of a sharp tip or 

 point on the opposite side of the globes, the stalk 

 seems to extend qi^iite through it. The fruit is 

 borne in a many times branched "twiggy," thick- 

 ened receptacle, which grows from the axils of the 

 leaves. I have found this plant growing common 

 upon small stones and pebbles all along our south- 

 ern New England coast, just below low-tide marks, 

 usually less than two feet long, though I have plants 

 not less than four feet. But the length will depend 

 mostly upon the age. Plants not more than a foot 

 long make the best herbarium specimens. It is peren- 

 nial. 



