82 POLYSIPHONIA. 



V. POLYSIPHONIA. Grev. [Plate 12, A.] 



Frond filamentous, partially or generally articulate ; joints 

 longitudinally striate, composed of numerous radiating cells 

 (siphons) disposed round a central cavity. Fructification 

 twofold, on distinct plants ; 1, ceramidia, containing a tuft 

 of pear-shaped spores ; 2, tetraspores imbedded in swollen 

 branchlets. Name, TTOMS, many, and <n<pcov, a tube. A vast 

 genus, of which nearly 300 species, from all parts of the 

 world, have been described ; many, probably, more than 

 once under different names. 



SUB-GENUS I. OLIGOSIPHONIA. Primary tubes four, rarely jive. 



* Frond articulated ; the articulations distinctly visible to the base of 

 the stem. 



1. P. urceolata, Sm. ; threads rigid, setaceous, much 

 branched, loosely entangled ; branches dichotomous, erecto- 

 patent, more or less furnished with short, patent, or recurved 

 ramuli ; joints bi-striated, those of the main branches 3 5 

 times longer than broad, of the ramuli very short; ceramidia 

 pitcher-shaped, with a produced, contracted mouth, generally 

 stalked. Harv. Phyc. Brit. t. clxvii. ; Hook. Br. Fl. ii. p. 

 330; Wyatt, Alg. Danm. No. 133. Conf. urceolata, E. 

 Bot. t. 2365. ft. patens. P. patens, Grev. Hook. 1. c. Conf. 

 patens, Dillw. t. G. 



On rocks, and the larger Algae, often covering the stems of Laminaria 

 digitata. Annual. Summer. Stems 3 9 inches high, dark red, as thick 

 as horse-hair at the base, loosely entangled in large bundles, scarcely at- 

 tenuated, rigid, not collapsing on removal from the water, and very imper- 

 fectly adhering to paper. Articulations very variable in length, in different 

 parts of the plant ; dissepiments broad and colourless. /3. is less branched, 

 with shorter joints, the branches beset throughout their length with short, 

 recurved ramuli. It is the P. patens of authors, and of ' British Flora,' 

 in which work I have expressed doubts whether it be specifically distinct 

 from P. urceolata. A longer acquaintance with the subject induces me, 

 unhesitatingly, to unite them. /3. is generally found on the stems of Lami- 

 naria digitata ; a. on rocks, but not invariably so. 



2. P. formosa, Suhr. ; threads exceedingly slender and 

 flaccid, much divided ; branches long, flexuous, bearing a 

 second or third series; ramuli scattered, spreading; joints 

 of the main branches many times longer than broad ; cera- 

 midia pitcher-shaped, with a produced contracted mouth. 

 P.formosa, Suhr.; Harv. Phyc. Brit. t. clxviii. P. graci- 

 lis, Grev. MSS. ; Wyatt, Alg. Danm. No. 216. 



