1925] Setchell-Gardner : Melanophyceae 531 



Key to the Genera 



1. Fronds solid and strap-shaped 2 



1. Fronds hollow and cylindrical, flattened, globose or difform 3 



2. Interior composed of hyphal tissue 25. Endarachne (p. 538) 



2. Interior composed of parenchymatous tissue 24. Hea (p. 535) 



3. Fronds cyhndrical or flattened 23. Scytosiphon (p. 531) 



3. Fronds globose or difform 4 



4. Membrane entire 26. Colpomenia (p. 539) 



4. Membrane reticulately perforated 27. Hydroclathrus (p. 542) 



23. Scytosiphon Ag. (emend. Thuret) 



Frond unbranched, solid when young, later tubular, cylindrical or 

 compressed, constricted at short intervals or smooth throughout, con- 

 sisting of two layers of cells, an inner of thick-walled, vertically 

 elongated, colorless cells, and an outer of small, rounded, cuboidal, 

 assimilating cells, the latter giving rise to the plurilocular gametangia 

 covering the entire surface, except at the base, and to scattered uni- 

 cellular paraphyses (?) and hairs when present; growth intercalary 

 near the base. 



Agardh, Dispos. Alg. Suec, 1811, p. 24 (fide Pfeiffer) (pro parte) ; 

 Thuret, Rech. sur les zoospores, 1850, p. 239. 



The genus Scytosiphon originally included what we now call 

 Dictyosiphon foenicidaceus, Chorda Filum and Scytosiphon Lomen- 

 taria. Thuret seems to have been the first to restrict the generic name 

 to the Chordaria Lonientaria Lyngbye and to point out the generic 

 characteristics. 0. Kuntze (1898, pp. 430 and 434) has proposed the 

 generic name Tuhicutis but the International Rules (Briquet, 1912, 

 p. 76) decided in favor of the retention of Scytosiphon. 



Scytosiphon Lomentaria (Lyngb.) J. Ag. 



Plate 44, figs. 72, 74 



Fronds usually fasciculate, sometimes solitary and scattered, 15-30 

 cm. (up to 60 cm.) high, 3-6 mm. diam., cylindrical, at intervals more 

 or less deeply constricted, attenuated below into a small solid stipe, 

 attached by a small disk ; color dark brown to olive green ; plurilocular 

 gametangia forming a compact palisade layer over the surface of the 

 frond; paraphyses (?) scattered among the gametangia. 



Growing on rocks in the whole of the littoral belt. Common along 

 the entire Pacific coast from Port Clarence, Alaska, to southern 

 California. 



