50 SEA MOSSES. 



mingled with it in tide pools and upon the rocks 

 between tides. They are distinguished from that by 

 their s??ialler and tubular fronds. There are three 

 American species of this genus, common everywhere, 

 on both sides of the continent, and easily distinguished 

 from each other. 



Enteromorpha intestinalis Link. 

 The first named species is a simple unbranched 

 frond. Very slender at the bottom, it gradually 

 expands to the width of half an inch or more, some- 

 times an inch and a half, and grows from six to ten 

 inches high. It keeps nearly of the same width 

 throughout. When found growing in the tide pools, 

 it will usually be seen to be inflated, or filled with air 

 bubbles. Being filled out in this way, and at the 

 same time a little constricted at irregular intervals, 

 it has a decidedly intestinal appearance. The color 

 is a light green, but portions of the frond, especially 

 at the top, will often be found colorless, or white, 

 owing to the fact that the chlorophyl, or green coloring 

 matter of the cells, has been discharged. The un- 

 branched inflated frond distinguishes this species. 



Enteromorpha compressa Grev. 



In this species the frond is compressed or flattened, 

 and is never inflated. The two layers of cells which 



