OLIVE COLORED ALG^E. 107 



at the base. A quarter of the way up it is bare. From 

 that point it is thickly beset all around with short 

 branches, varying from half an inch to one and one- 

 half inches long, undivided, narrowly constricted at 

 the base, blunt at the apex, mostly curved, and stand 

 out perpendicularly from the main stem. 



Genus.— CASTAGNEA, Thuret. 



Castagnea Zosterte, Thuret. 



This species is named from the "Eel grass" or 

 Zostcra, on the fronds of which it commonly grows. 

 It is a very slender plant, not larger than a thread or 

 bristle, and some six or eight inches long, of a light 

 olive color, somewhat bent in a zigzag way, and but 

 sparingly branched. The brandies are irregularly 

 placed, short (about one inch long), spreading horizon- 

 tally from the main stem, and either widely forking 



beset with twig-like brahchlets, which are also fre- 

 quently forked or spiney. It adheres nicely to paper, 

 and is not an uninteresting though by no means a 

 handsome plant. I found it in August, in Marblehead 

 harbor. My correspondents do not report it else- 

 where, though Dr, I'arlow records it in Wood's Holl, 



