NO. 1 DAWSON: MARINE RED ALGAE OF PACIFIC MEXICO 13 



30. Tetrasporangia solitary from each bearing cell; basal 

 cell of determinate laterals about the same length as 



the others 31 



31. Plant about 2 mm high; tetrasporangia essentially confined 



to basalmost cell of determinate laterals 



A. basisporum Tokida & Inaba 



31. Plants up to 1.5 cm high; tetrasporangia not confined to 



basalmost cell of determinate laterals (2-3 lower cells) 32 



32. Tetrasporangia tetrahedrally divided; gland cells sparse 



A. miharai Tokida (in part) 



32. Tetrasporangia cruciately divided, but often appearing 

 as if tetrahedrally divided; gland cells frequent, often 



on adjacent cells, but sometimes apparently absent 



A. glanduliferum Kylin 



33. Gland cells absent; tetrasporangia pedicellate 



A. floccosum (Miiller) Kleen 



33. Gland cells present 34 



34. Determinate branchlets 20 p. diameter; tetrasporangia 



sessile A. veleroae Taylor 



34. Determinate branchlets 80 fi diameter; tetrasporangia 



pedicellate A. dendroideum Sm. & Hoi. 



35. Gland cells absent or unreported 36 



35. Gland cells present 39 



36. Thalli minute, less than 1 cm high 37 



36. Thalli macroscopic, 3-4 cm high .... A. nigricans Gardner 



37. Determinate lateral branches in whorls of 4 



A. dumontii Dawson 



37. Determinate lateral branches in whorls of 3 (sometimes 4) .... 38 

 38. Tetrasporangia very large; plants 1-2 mm high, sparsely 



branched; Tongatabu A. graffei (Grunow) DeToni 



38. Tetrasporangia unknown; plants to 8 mm high, abun- 

 dantly branched; Gulf of California 



A. mcnabbii Dawson 



39. Terminal cells of lateral branchlets acute 40 



39. Terminal cells of lateral branches blunt 43 



40. Branchlets tapering abruptly at the tips 41 



40. Branchlets not tapering abruptly at the tips 42 



41. Successive verticils overlapping A. densiusculum Gardner 



41. Successive verticils not overlapping A. baylesiae Gardner 



42. Branchlets secund throughout, tapering to acute tips .... 



A. subulatum (Harv.) J. Ag. 



42. Branchlets secund above, becoming pinnate below, sub- 

 ulate, with acute tips A. corallina (Rupr) Kjellm. 



