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BULLETIN OF THE BUREAU OF FISHERIES. 



cases. The characters which are most useful for separating the species and have been 

 used by recent authors are the mutual arrangement of the son and the lines of hairs, 

 the presence or absence of an indusium covering the son, and the number of cell layers 

 in the thallus. 



Pig. 30. Elachislea slellulata, internal filaments branched Fig. 22. Padina vickersue, cross section of thallus, X 273. 



and anastomosed, X a?3- Fig. 23.Goniotrickum alsidii, X 300. 



Fig. 2i.Elachistea steUulata, external filaments and "plu- Fig. nErythrotrichia cornea, cells forming spores, X .<oo. 

 rilocular sporangia, " arising from basal disk as seen in optical 

 section, X 273. 



Padina vickersise Hoyt. Fig. 22; PI. XCII, figs, i and 2; PI. CXIV, figs. 1-3. 



Zonaria variegata, Kuetzing, 1859, Bd. 9, p. 30, pi. 73. fig- * 



Padina variegata, Vickers, 1905, No. 66. 



Padina variegata, Vickers, 1908, pi. 8. 



Padina mckerstai, Hoyt, in Britton and Millspaugh, 1920, p. 595. 



Thallus erect, flat, expanded, 4 to 22 cm. tall, 5 to 37 cm. broad, entire when young, when mature 

 repeatedly more or less deeply laciniate from the margins into segments, varying from cuneate spatulate 

 to fan shaped, sometimes incrusted with lime, zonate by piliferous lines parallel with the margins, 

 often becoming inconspicuous in the older parts, interpilar zones 1.5 to 6 mm. wide, base consisting 

 of a thickened, rounded stipe 3 to 12 mm. long, densely covered with brown rhizoids, attached by a 

 basal disk; lamina consisting of 3-cell layers near re volute apical margins, of 4-cell layers throughout 

 most of thallus, and of 6 to 8 cell layers toward the base, epidermal cells about half as long as the central 

 cells; tetrasporangia covered by a thin, subpersistent indusium, borne on both surfaces, usually pre- 

 dominantly on the lower surface, occurring in i to 2 lines parallel with the apical margin about the 

 middle of each interpilar zone, these lines frequently being broken, the tetrasporangia being scattered 



