RHODOMELACEJE. 97 



bright beads of water give to the whole plant a tran- 

 sient gleam of radiance that is very charming. 



Genus XLI. POLYSIPHONIA. 



Fronds thread-like, rarely a little flattened, jointed, or 

 with a jointed axis, composed of elongated tubular cells, 

 arranged round a central cell. Spores pear-shaped, in 

 ovate or nrn-shaped conceptacles ; tetraspores (of British 

 species) tripartite, imbedded in distorted, terminal branch- 

 lets. — PoLTSiPHoyiA, from the Greek pohis, many, and 

 siphon, a tube. 



This genus contains, according to various writers, be- 

 tween two and three hundred species, which are distri- 

 buted in almost every latitude between the poles and 

 the equator, and vary much in size and in external ap- 

 pearance. Dr. Harvey describes it so admirably in 

 his ' Nereis Boreali-Americana/ that I shall quote his 

 words. He says: — "Some species are two to three 

 feet in length, others not more than as many tenths 

 of an inch; some dichotomous, others pinnated —some 

 distichous and fern-like, others with a bushy or arbores- 

 cent character ; some of cobweb delicacy, lubricous, and 

 excessively flaccid, soon decomposing, others robust, rigid 

 or tough, of strong enduring substance; some of a brilliant 

 rosy- red or crimson, others (and the greater number) 

 varying through all the graver shades of red-brown, 

 brown, and purple ; some inhabiting the deep sea, 

 others occurring only near high-water mark or far up 

 the estuaries of tidal rivers. Plants of such varied 

 aspect and habit could not have been brought together 

 by the universal consent of botanists, among whom 

 there has never been much difference of opinion re- 

 specting the just limits of this genus, if they had not 



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