(66) 



Description. — Root, a minute disc. Stem elongate, one to two inches 

 or more in length, cylindrical at the base, but soon becoming compressed 

 and at length flattened, dichotomously divided into a broad flabelliform 

 frond, much tufted, two to five inches or more in height, and as much in 

 breadth ; the segments broad and obcuneate, and flat or narrow, linear 

 and compressed, but exceedingly variable in breadth, generally from one 

 line to one inch or upwards ; in the broad varieties with wide rounded 

 axils, and the segments greatly expanding upwards and overlapping at 

 the apices, which are obtuse or emarginate. Occasionally the margins, 

 especially in old or injured specimens, are more or less fringed with 

 small leaf-like processes. Structm-e : axis occupying fully two-thirds 

 of the frond, fibro-cellular, composed of very slender articulated fibres, 

 densely packed and interlaced ; from these arise larger, less densely 

 packed cells, imperfectly arranged in filaments, becoming smaller towards 

 the circumference, where they are very minute, and regularly moni- 

 liform. Substance cartilaginous, readily dissolving into gelatine by 

 boiling in fresh water. Colour, a dark reddish brown, which readily 

 changes to a yellowish green on exposm-e to air and light even when 

 growing, and quickly bleaching to a dull transparent white after 

 being gathered and exposed. Tetraspores forming roundish oblong 

 sori, imbedded in the substance of the frond, occasionally concave on 

 one side. 



One of the most polymorphous of British Alga), growing on almost 

 every " soil and situation " wdthin tide range, and to a considerable 

 distance beyond it, on the larger Algee as well as on rocks, stones, and 

 even wood, often growing in scattered tufts among G. mamillosiis, and 

 sometimes covering rocks by itself, generally having the stems half 

 imbedded among the small mussels. The upper portion of the frond is 

 of a yellowish green colour, while the lower part is of the original dark 

 purple, which colour pervades the whole plant when not exposed to the 

 light. 



When growing in "brackish water the fronds are sometimes of large 

 size, rather soft and flaccid, the segments very broad and crisped, the 

 surface rough and areolated. On this variety we have seen no fruit. 



The fronds are at first cylindrical, simple, then compressed, emarginate, 

 bifurcate, and at length flat and repieatedly dichotomous, the dicho- 

 tomies being seldom of equal length, and the ultimate ones short and 

 obtuse or emarginate. 



This is one of the few plants upon which man has condescended to 

 confer a local name, being the Carageen or Irish moss of the shops, where 

 it is sometimes purchased as a light diet for invalids. It was first used, 

 perha^js, in Ireland, hence its by no means appropriate name of Irish 



