56-i FRESH-WATER ALG^. [LicdomacecB, 



lobed segments ; the lobes inciso-dcutate (rarely only bidentate) 

 and generally radiant. — Ralfs. 



1. MiCRASTERiAS DENTicuLATA, BreUssoii. (Plate XX. 

 fig. 80, a mature frond, and under it a dividing frond.) 



Hab. Penzance, Mr. Ealfs ; Kent, Mr. Jcnner ; Henfield, 

 Mr. Borrer ; Bristol, Mr. Broome ; Ambleside, Mr. Side- 

 botliam ; Aberdeenshire, Dr. Dickie ; Stevenston, in Ayr- 

 shire, D. L. 



This species is not uncommon. It is found in marshy 

 ground and in ditches. The frond is large and nearly 

 circular, each segment is five-lobed ; the colour is bright 

 green; frequently the margin of the frond is colourless. 

 Originally the two segments of the frond are united by a 

 narrow tube, as seen in the plate. This connecting tube 

 lengthens, expands, and becomes two young segments, of a 

 lighter green colour, as in the lower figure. When these 

 two segments have become full -sized, they separate, and 

 form two fronds, of each of which one half is old, and the 

 other half new. 



HYALOTHECA, Ehrenherj. 



Gen. Char. Filament elongated, cylindrical, very gelatinous ; 

 joints having either a shght constriction, which produces a 



