110 
CLASS II. — ORDER I. 
They are found in thick tufts on rocks and solid 
bodies ; in the first stage of their development, the 
tube attains its full size, and the umbel is about one 
line in diameter ; by little and little this umbel en- 
larges, and soon acquires its full size ; when it has 
reached this point, it only increases in thickness, and 
soon after perishes ; for many circumstances induce 
the belief that these Polypidoms have not a long 
existence. In the sea the stems are flexible, gelati- 
nous, and of a greenish colour ; the disks sometimes 
display a very brilliant shade of green. By desiccation 
some of these characteristics disappear, the polypidom 
becoming very fragile, and nearly white. 
The Acetabularia seldom reach a decimetre in 
height ; they are found in the tropical and temperate 
seas of both hemispheres. 
MEDITERRANEAN. 
1. Acetabularia Mediterranean Umbel with an 
even border. 
Mediterranean. 
CRENATED. 
2. Acetabularia crenulata . Umbel with a 
crenated border. — Plate 8. fig. X. 
Seas of Antilles. 
