6 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 26 



5. Longer pair of lateral branchlets bearing subultimate branchlets 



only on the upper side 7 



5. Longer pair of lateral branchlets bearing 1 row of branchlets 



on the upper side and one on the lower side 6 



6. Adaxial ultimate branchlets tending to develop earlier and 

 to be more prominently developed; spermatia in low, 



mounded clusters, the spermatangia of 1-2 cells 



P. orbigniana (Mont). J. Ag. 



6. Adaxial ultimate branchlets tending to be more prominantly 

 developed; spermatia in elongated, cylindrical clusters, the 



spermatangia of 2-3 cells P. tepocensis Dawson 



7. Branchlets all very short, spine-like 



P. horridum Tokida & Inaba 



7. Branchlets ± subulate, not especially short 8 



8. Smaller pair of lateral branchlets not much smaller than 



larger pair P. intermedium Tokida 



8. Smaller pair of lateral branchlets very markedly dwarfed, 



shorter or less developed than the larger pair 9 



9. Smaller pair of lateral branchlets simple to multifariously 



branched from the basal cell P. pectinatum Kylin 



9. Smaller pair of lateral branchlets pinnately branched 



P. yezoensis Inagaki 



Platythamnion pectinatum Kylin 



PL 1, fig. 4 a-c; PI. 4, fig. 2-3 



Kylin 1925, p. 53, fig. 32D, 33E, 34A-C; Smith 1944, p. 316, pi. 79, fig. 1; 

 Platythamnion pectinatum var. laxum Taylor 1945, p. 226. 



Thalli 1-2 cm in extent or more, the lower parts partially 

 prostrate, attached by multicellular branched rhizoids; principal axes 

 irregularly branched at intervals of 3-7 cells, 150-200 fi in diameter, 

 mostly of cells 1-1.3 diameters long and approximately equal above and 

 below; all principal axes provided at each axial cell node with 4 

 determinate branches of 2 kinds: one opposite pair of compound, 

 ascending, long laterals and an opposite pair of shorter dwarf laterals; 

 long pair of determinate laterals of about 9-12 cells 22-24 \i in diameter 

 at the base and about 2 diameters long, sharply pointed, sometimes 

 attenuated, the cells of approximately equal proportions except the 

 basalmost which is somewhat shorter, provided with branchlets only 

 on the adaxial side: usually 2 compound branchlets from the first 2 or 

 3 cells and a single compound or simple one from the next 4 or 5 

 cells; all ultimate branchlets from the adaxial side of the bearing 

 branchlet, sharply pointed; short determinate laterals consisting of a 

 subspherical basal cell usually bearing 3 (5-6) simple or forked com- 

 pound branchlets, the uppermost one longest, often of 5 cells; gland 



