SECT. n. SAEGASSUM. 257 



hemisphere among them the Hormoseira, in which 

 the frond, at first even and filiform; becomes inflated so as 

 to produce moniliform chains of vesicles, parts of which 

 are at length rough with the apertures of the concep- 

 tacles ; this plant has bladder-like air-vessels formed by 

 swollen parts of the frond, like many of our Fucacese. 



Those genera which have distinct organs containing 

 air, as the Sargassum, of which there are numerous 

 species, are either of low latitudes or tropical, but are 

 sometimes drifted by currents to the extra-tropical 

 shores. The Sargassum vulgare, however, grows on the 

 rocks in the Mediterranean. The whole plant is of a 

 translucent reddish brown ; the stem has alternate 

 branches, bearing lanceolate serrated leaves with a 

 midrib, and generally dotted with dark pores. The air- 

 vessels are small translucent round balls about the size 

 of a currant, borne on flat stalks in the axils of the 

 branches, and the spores are in conceptacles borne on the 

 branchlets just above the air-vessel. In one variety of 

 this most variable plant, the Uva di mare, the main 

 stem ends in a loose bunch of these little air-balls. 



The Sargassum bacciferum is often found in the 

 Mediterranean, but only as a wanderer drifted in from 

 the Atlantic, where masses of it, like floating meadows, 

 occupy an area west of the Azores equal in extent to that 

 of Prance, which has never changed its position since 

 the time of Columbus, on account of the surrounding 

 currents. Fields of it cover the seas near the Bahama 

 Islands, and another permanent area of Sargassum of 

 great extent occurs in the South Pacific. The Sargassum 

 bacciferum is of a pale translucent olive colour, having 

 branched stems, with lanceolate, midribbed, and serrated 

 leaves, destitute of pores, and little stalked air-balls in 

 the axils of the branches. The same individual con- 

 tinually produces new branches and leaves, and thus 

 multiplies its species, but it never produces fruit ; conse- 



VOL. I. 8 



