118 BRITISH SEA-WEEDS. 



branchlets few, tapering at each end. Spores minute, in 

 large, roundish, stalkless conceptacles plentifully scattered 

 over the branches; tetraspores minute, embedded in the 

 surface cells of the branches. 



This species is perennial, and attains its greatest luxu- 

 riance during summer and autumn. It is found plenti- 

 fully all round our coasts^ and is readily distinguished 

 by its prominent spore-conceptacles, which have the ap- 

 pearance of knots on the slender branches. The colour 

 is a dull purple, which fades to white when the plant 

 grows in shallow places, or is exposed to the air and 

 light. When dry it is rigid, and does not adhere closely 

 to paper. Dr. Harvey speaks of a variety found in 

 American waters, which is destitute of branches, and 

 reaches the length of six feet. I am not aware that 

 anything approaching this has been found on our coasts. 



Genus LV. SPH^ROCOCCUS. 



Frond horny, compressed, linear, two-edged, forkedly 

 branched, composed of three series of cells ; those in the 

 centre, which form a kind of internal rib, fibrous and 

 densely packed, the next series large and many-sided, 

 and those on the surface minute and thread-like. Spores 

 minute, arranged on a central placenta in spherical con- 

 ceptacles ; tetraspores, according to Kiitzing, zonate, scat- 

 tered through the substance of the frond. — SpHLSEOCOCcrs, 

 from the G-reek sphaira, a sphere, and coccos, fruit. 



Sphaerococcus coronopifolius. The buck's-horn 

 Sphaerococcus. 



Eronds from a few inches to a foot or more long, much 

 branched ; main stems thickened and two-edged below, be- 

 coming thinner and flatter in their upper parts, irregularly 



