NO. 1 TAYLOR: PACIFIC MARINE ALGAE 209 



anticlinal rows and certain other peculiarities, such as markedly large 

 cells at each forking of these rows, and pyriform surface cells. DeToni 

 (1915, pp. 1586, 1594) considers that Prionitis has three structural zones 

 and Polyopes two. No fruit appears in the present material; so nothing 

 can be done about a more critical estimate of the generic position of the 

 species from that aspect. 



Mexico: Baja California, on rocks at South Bay, Cerros, no. 34- 

 647, 10 Mar. 1942. 



PRIONITIS J. Agardh, 1851 

 Thallus compressed or flat, linear, dichotomously or pinnately 

 branched with frequent adventitious lateral branchlets ; firm to subcarti- 

 laginous; inner cortex lacunose within and penetrated by rhizoids, out- 

 wardly of enlarged rounded cells, the outer cortex of small cells in anti- 

 clinal rows; tetrasporangia in special lateral branchlets with thickened 

 cortex, tetrapartite ; cystocarps scattered on special fertile branchlets, im- 

 mersed, projecting more or less into the medulla, surrounded by a rela- 

 tively feeble filamentous pericarp. 



KEY TO SPECIES 

 1. Axis and branches terete to a little compressed 2 



1. Branches flat, subfoliar 3 



2. Larger, 1-4 dm tall, the main axes subdichotomous, bearing ir- 

 regular to pinnately disposed slender branchlets . . P. filiformis 



2. Small, to 2 cm tall, dichotomously branched, complanate, with 

 small adventitious branchlets bilaterally disposed below P. kinoensis 



3. Dichotomously branched, the segments strap shaped, little taper- 

 ing, with abundant adventitious branchlets on the margins of the 

 segments ^ 



3. Segments linear lanceolate, with rather acute tips .... 5 



4. Adventitious branchlets ligulate P« abbreviata 



4. Adventitious branchlets spatulate to reniform . . P. Hancockii 



5. Irregularly dichotomous throughout, the blades plane or nearly 



gQ P. albemarlensis 



5. Dichotomous below, but the upper portions pinnate, the blades 

 markedly crisped P- galapagensis 



Prionitis filiformis Kylin 

 Plants to 45 cm tall, below freely alternately or irregularly subdichot- 

 omously branched, the upper segments long, sparingly to closely bilater- 

 ally beset with linear oblanceolate branchlets 5-10 mm long; major axes 



