152 BRITISH SEA-WEEDS. 



like excrescences ; tetraspores cruciate, formed in the upper 

 branclies. — Poltides, from the Greekpolus, many, and idea, 

 form. 



Polsrides rotundus. The round Folyides. 



Fronds growing several from the same base, from two to 

 six inches high, forkedly divided, of a cartilaginous sub- 

 stance, and dark red-brown colour, not adhering to paper. 



This species is the only one contained in the Order, 

 and is very distinct from all the British Sea-weeds ex- 

 cept Furcellaria fastigiata, which it resembles so closely 

 in external appearance that it is difficult to believe that 

 the two are reaUy so different in structure. There is, 

 fortunately, one very simple character by which they 

 may be identified : the root of P. rotundus is a small 

 disc ; that of F. fastigiata is fibrous. The former is, 

 moreover, much less common than the latter. P. rotun- 

 dus grows on rocks in tide-pools and in deeper water. It 

 is perennial, and attains perfection in winter ; but may 

 be found at other seasons. 



Order XIV. SQUAMARI^. 



Lichen-like, incrusting or horizontally expanded, Red-hrown 

 Sea-weeds, rooting hy the under surface, composed of ver- 

 tical filaments closely set in firm gelatine. Spores in 

 necklace-like strings, lodged in wart-like excrescences, 

 formed of vertical filaments. 



Genus LVIII. PEYSSONELIA. 



Erond membranous or leathery, horizontally expanded, 

 and attached by fibrils emitted from the lower surface, com- 

 posed of two strata of cellules : those of the lower stratum 

 horizontal, elongated, cylindrical, arranged in radiating fibres, 

 which are placed close together, and form a membrane ; those 



