1925] Setchell-Gardner: Mehinophyceae 613 



45. Thalassiophyllum Post, and Riipr. 



Holdfast of stout, diehotomously branched hapteres ; primitive 

 stipe short, not elongating but thickening, soon buried among the stout 

 hapteres ; blade soon eroded to the base and developing two lateral 

 scrolls which unroll as they develop from thickened margins and form 

 fan-shaped, spirally twisted, closely and regularly perforated, partial 

 blades ; numerous secondary stipes or branches, arising along the 

 thickened margins, bearing small blades ; no mucilage ducts in either 

 the stipe or blade ; sori in irregular dark brown areas ; plants perennial. 



Postels and Ruprecht, Illus. Alg., 1840, p. 11. 



There are two peculiarities of the genus ThalassiopliijUum, viz., 

 the one-sided fan-shaped blades unrolling from a one-sided scroll, 

 borne on M'hat seems to be a branched, heavy, solid stipe. From the 

 development (cf. Setchell, 1905a, p. 123, pi. 13, figs. 6-13) it appears 

 that the early stages resemble those of Agarnm in being bilaterally 

 symmetrical, with basal margins inrolled. By the disintegration of 

 the central portion of the blade, the basal margins only are left with 

 their scrolls. One margin ceases to develop, as does the short primi- 

 tive stipe. The other basal margin thickens, elongates, and becomes 

 stipe-like, bearing its one-sided blade. The branches (false) arise 

 (cf. Rosenthal, 1890, Flora, vol. 73, pp. 140, 141, pi. 8, figs. 33, 34) by 

 adventitious outgrowths from the developing scroll-like base of the 

 blade. The branching of ThalassiopliyUum is a pseudo-branching and 

 of a pseudo stipe not to be confounded with that of the Lessoniaceae 

 or in Egregia of the Alariaceae. 



Thalassiophyllum Clathrus (Gmel.) Post, and Rupr. 



Plate 72- 



Plants 12-15 dm. high, rigid ; holdfast and stipe as in the genus ; 

 blade thick and coriaceous, with the numerous, large elliptical per- 

 forations with roughened margins radially arranged ; color dark 

 brown to deep olive green, much darker toward the basal portions. 



Growing on rocks in the sublittoral belt. Bering Sea to the Straits 

 of Juan de Fuca (the last mentioned locality fide MacMillan, 1902, 

 p. 219). 



Postels and Ruprecht, Illus. Alg., 1840, p. 11, pis. 18-19; Setchell, 

 Alg. Prib. Isl, 1899, p. 592, Post-emb. Stages, 1905a, p. 123, pi. 13, 



