NO. 2 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 265 



scattered through the cortex which shows no nemathecial modification, 

 cruciate, ovate, about 18 /x long, 9 /x wide; sexual reproduction unknown. 



Type: Holotype is Taylor 39-656, May 9, 1939, on sheet 7020 in 

 HAHF. 



Type locality: At a depth of 22 m. on a coralline algal bottom, 

 N. Lat. 21° 25' 40'^ W. Long. 106° 21' 10'', off Isia Maria Mag- 

 dalena. Las Tres Marias, Nayarit, Mexico. 



Although tetrasporangia occur in the type specimen, this species was 

 described from sterile material and apparently assigned to Cryptonemia 

 on the basis of habit and vegetative structure. It is retained here because 

 of the similarity of its structure and tetrasporangia to the other Mexican 

 species here treated as Cryptonemia. 



Key to the Mexican species of Polyopes 



1. Thalli 5-10 cm. high; upper segments 1.5-2,5 mm. wide, 150- 

 300 ix thick; ultimate segments short ... P. bushiae 



1. Thalli 2.5 cm. high; upper segments 1.0-1.5 mm. wide, 125- 

 150 /A thick; ultimate segments long . . P. clarionensis 



Polyopes bushiae Farlow 

 P1.2, figs. 16-18 ; PI. 11, fig.55 



Farlow 1899, p. 75; Kylin 1941, p. 11 ; Taylor 1945, p. 208; Daw- 

 son 1950a, p. 68; Dawson 1951, p. 53. Cryptonemia bushiae nom. nud. 

 in Collins, Holden and Setchell, P. B. A. no. 600. 



Thalli 5-8 (10) cm. high, usually bushy, rather rigid, deep, dull red 

 in color, perennial, consisting of repeatedly dichotomous ligulate blades 

 from one or more cylindrical stipes attached by a horny, discoid holdfast; 

 stipes 1.5-2.0 mm. in diameter, cylindrical below, flattened above and 

 gradually transformed in the course of the first 2-3 dichotomies into the 

 flattened segments ; branching primarily dichotomous at intervals of 3-9 

 mm., above sometimes irregularly pinnate-proliferous to a limited extent; 

 segments 1.5-2.5 mm. broad, mostly 150-300 /* thick, entire, cartilagin- 

 ous, the terminal ones blunt; structure as seen in transection consisting 

 of a central medullary tissue of densely packed, intertwined, ramified, 

 fibrous filaments 3-5 fx in diameter, an outer medullary and subcortical 

 tissue of thick-walled, ± rounded cells mostly 9-14 /x in diameter, and a 

 pigmented cortex of anticlinally arranged filaments of about 4 small, 

 elongate cells 3-5 /x broad ; tetrasporangia borne abundantly in the cortex 

 which is prominently nemathecially modified on both flattened surfaces 



