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 Mediterranea. Umbel with an 

 even border. 



Mediterranean. 



CRENATED. 



2. Acetabularia crenidata. Umbel with a 

 crenated border. — Plate 8. fig. 1. 



Seas of Antilles. 



