214 BRITISH SEA-WEEDS. 



These small gelatinous sea- weeds resemble the fresh- 

 water Batrachospermm more nearly than any salt-water 

 genus. One species only has been found on our coasts, 

 and that one very rarely. 



Crouania attenuata. The attenuated Crouania. 



Frond tufted, one to two inches long, very delicate and ge- 

 latinous, much branched ; branches attenuate, jointed, the 

 whole frond whorled at the nodes with minute, forked, fas- 

 tigiate branchlets. Tetraspores cruciate, solitary ; favellaB not 

 seen on British specimens. 



This exquisite little plant is extremely rare, and has 

 never been collected in great abundance anywhere. It 

 is parasitic on small sea-weeds, and has been found on 

 Cladostephus spongiosus. When young the ramelli ap- 

 pear to clothe the stem and branches like a bark, but as 

 the joints lengthen they separate into distinct whorls. 

 The tetraspores are very large in proportion to the size 

 of the plant. 



Genus XCXIX. HALTTRTJS. 



Frond thread-like, jointed, single-tubed, irregularly di- 

 vided, with short, incurved, forked branchlets whorled 

 round aU the nodes. Spore-clusters borne on the tips of 

 shortened branches, surrounded by involucral branchlets ; 

 spores angular, numerous, contained in a transparent 

 envelope; tetraspores spherical, tripartite, borne on the 

 inner sides of the forked branchlets of an involucre. 



The plants which compose this genus were formerly 

 included with the Griffithsim. Only two species have 

 been described, and but one of these is found on our 

 shores. 



