652 University of California Publications in Botany [Vol. 8 



IVEY TO THE SpECIES 



1. Margin of the frond profusely toothed and crenulate 5. D. crenulata (p. 655) 



1. Margin of the frond smooth 2 



2. Fronds large, 1.5-2.5 dm. long, 250-500/i thick, axils rounded 5 



2. Fronds smaller, up to 15 cm. long, axils more or less acute 3 



3. Fronds 7-9 cm. long, 135-160^ thick, axils wide 4. D. Vivesii (p. 654) 



3. Fronds 8-15 cm. long, 80-135/i thick, axils narrow, acute 4 



4. Oogonia single 6. D. hesperia (p. 655) 



4. Oogonia collected into sori 3. D. Johnstonii (p. 653) 



5. Fronds dark brown, coriaceous, tips rounded 1. D. Binghamiae (p. 652) 



5. Fronds pale yellowish brown, deUcate, tips truncate 2. D. flabellata (p. 652) 



1. Dictyota Binghamiae J. Ag. 



Plate 34, figs. 1, 2 



Fronds 10-18 cm. (up to 25 cm.) high, with stupose base of fine 

 brown hairs, closely appressed, extending for some distance up the 

 frond, coriaceous below, up to 500ja thick, thin and membranaceous 

 above, branches strict, angles rounded, terminal lobes rounded ; color 

 dark below, brown above. 



Growing in pools in the middle and lower littoral belts. Southern 

 California and northern Lower California (Ensenada). 



J. G. Agardh, Anal. Alg. Cont. I, 1894, p. 72 ; Collins, Holden and 

 Setchell, Phyc. Bor.-Amer. (Exsicc), no. 1392. Dictyota Kunthii 

 Farlow, Kept. U. S. Fish Comm., for 1875, 1876, p. 705; Farlow, 

 Anderson and Eaton, Alg. Exsicc. Amer.-Bor., no. 93. Glossophora 

 Kunthii Collins, Holden and Setchell, loc. cit., no. 85. 



This is a large and broad, coarse species with even margins and 

 rounded axils. In color it is usually darker brown than the next 

 species, somewhat thicker and more coriaceous, more truly dicho- 

 tomous above, and with the upper lobes longer and more rounded. 



2. Dictyota flabellata (Collins) S. and G. 



Plate 34, fig. 3; plate 35, fig. 7, and plate 36, figs. 13-17 



Fronds plane, membranaceous, slightly stupose at the base, dicho- 

 tomous, or in mature plants certain segments growing faster than 

 others, presenting the appearance of being a flexuose rhachis with alter- 

 nate branching, 1-2 dm. high ; segments cuneate, widening upward to 

 each forking, terminal lobes and sinuses rounded; width variable, 2 

 mm. to 2 cm. wide ; color yellowish brown, darker toward the base ; 

 medulla consisting of a single layer of nearly cuboidal, colorless cells. 



