46 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



monosporangial branch; but that on the left seems unreal and probably 

 represents an erroneous interpretation of a monosporangial branch sup- 

 posed by him to be an antheridial one. Actually, the antheridial sorus of 

 S. johnstoniae is quite identical both superficially and anatomically with 

 that of S. articulata Setchell as illustrated by Dawson, 1949a, pi. 7, figs. 

 44-45. 



Scinala latifrons Howe 



Plate 4, fig. 1 



Howe, 1911, p. 500, text fig. 1, pi. 38; Setchell, 1914, p. 102, pi. 11, 

 figs. 2-3; Dawson, 1944, p. 258; Dawson, 1949, p. 237; Taylor, 1945, 

 p. 148. 



Thalli 10-20 cm. high, rose red in color, attached to a stone or a shell 

 by a small discoid holdfast 2-3 mm. in diameter from which a short terete 

 stipe 2-5 mm. long gives rise to a richly dichotomously branched frond, 

 complanate, the segments 5-10 mm. broad and 1.5-3.0 cm. long, about 

 150-200 /A thick in the thin mid-parts, thicker at the margins; structure 

 consisting of a colorless epidermis of anticlinally elongated utricles 18-29 

 p. broad by 33-45 /^ high, and a hypodermal layer of small, globose, pig- 

 mented cells arising from the filamentous medulla; plants dioecious; 

 antheridia in dense, continuous sori occupying the entire marginal area 

 of the thallus from base to near apex and also in small scattered patches 

 on mid-parts of the segments, arising from filaments sent up between the 

 utricle cells from the pigmented hypodermal layer; cystocarps conspicu- 

 ous, forming macroscopic dark spots aggregated along the thickened mar- 

 gins of the frond ; monosporangia not observed. 



Type: Holotype is G. J. Vives 11a, Feb. 28, 1911 in the Her- 

 barium of the New York Botanical Garden. 



Type locality: Near La Paz, Baja California, Mexico. 



Mexican distribution: Pacific Baja Calif. — D. 9490, Punta 

 Abreojos, Apr. Gulf of Calif. — This is a common species throughout the 

 Gulf of California in the upper sublittoral, occurring in a large propor- 

 tion of the shallow dredge-hauls made to date in that area. Antheridial 

 plants have been taken at Guaymas and at Isla Tiburon in January. 

 Nayarit — Taylor, 39-645, Isla Maria Magdalena, May. 



The detection of several antheridial plants among the collections 

 from the Gulf has revealed that the antheridia normally are quite unlike 

 those described and illustrated by Setchell (1914) for various species of 

 Scinaia, including the complanate S. cottonii. Neither is the species 



