Fig. 121. POLYSIPHONIA NIGRESCENS. 



Colour. A dull brown, sometimes a purplish red; old plants becoming black; all, 



darker in drying. 

 Substance. Rigid below; soft and delicate above. 



Character of Frond. Long tufts of jointed threads (^filaments), very much and 

 variously branched. Stems robust, nearly simple; sometimes set throughout 

 with richly feathered branches. In autumn and winter rough below with broken 

 remains; bushy above. Branches long, alternate; repeatedly re-branched in a 

 feather-like manner {pinnate); the sets becoming gradually more and more 

 slender. Branchlets short, alternate, distant below; the uppermost otten 

 crowded together; mostly simple, avvl-shaped. Joints closely marked with 

 numerous upright lines (internal tubes). 



Internal Tubes. From twelve to twenty. 



Measurement. From 6 to 8 inches long. 



Fructification. Of two kinds. 1. Clustered spores in broadly ovate, unstalked cap- 

 sules, with a narrow opening; external. 2. Tetraspores immersed in the lesser 

 branchlets. 



Habitat. All round our coasts. On rocks, stones, and algse between tide-marks. 

 Very common. 



Summer specimens are feathery and beautiful; autumn and winter ones coarse 

 and bushy. But, independently of this, it is one of the most variable of sea- 

 weeds. l3r. Harvey considers its "distantly pinnate" branchlets, and the great 

 number of its tubes sufficiently characteristic marks, but he has recorded seven 

 American varieties, and Britain could add more. In one short stiff form it 

 assumes the characters of Bytiphlcjea thuyoides so strongly, that nothing but 

 the microscope can separate them. (See under Bytiphloea thuyoides.) 



Fig. 122. POLYSIPHONIA AFFINIS. 



Colour. A dull, pale, reddish-brown. 

 Substance. Firm below; soft above. 



Character of Frond. Long tufts of jointed threads {Jilame^its) much branched. 

 Stems as thick as bristles below; irregularly forked; or alternately branched. 

 Branches spreading; naked at base, finely divided and ovate in outline above; 

 lesser branchlets all naked at base; furnished above with a few very upright, 

 alternate, or secund branchlets, the lowermost longest. Joints of the stem 

 obscure; those of the branches obvious; marked with numerous upright lines 

 (internal tubes). 



Internal Tubes. About sixteen. 



Measurement. From 4 to 8 inches long. 



Fructification. Of two kinds. 1. Clustered spores in ovate or nearly globose, stalked 

 capsules; external. 2. Tetraspores large; immersed in the lesser branchlets. 



Habitat. Clamlough, near Glenarm, Ireland. Cushendall, ditto. On rocks, &c. in 

 the sea, and thrown up from deep water. 



Dr. Harvey considers this almost too closely allied to P. nigrescens. Its 

 branching is more loose, its internal tubes fewer, its colour paler, its branches 

 more wavy, and its substance softer. Yet he could be "well contented to 

 regard it as a deep-water form of that species." Nevertheless, figures of the 

 typical forms of each are different. (See the figures.) 



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