no. 1 dawson: marine red algae of pacific mexico 151 



Key to the Mexican Species of Bossea 



1. Branching entirely, or at least predominately dichotomous . . 2 

 1. Branching entirely, or at least predominately pinnate ... 5 

 2. Plants with coarse, prominent, terete stipes; intergenicula 

 usually conspicuously thick . . . . B. pachyclada 

 2. Plants without coarse, prominent stipes; intergenicula not 



conspicuously thick 3 



3. Intergenicula more or less sagittate, with acute, distally project- 

 ing wings; branching more or less strictly dichotomous, often 



divaricate B. orbigniana 



3. Intergenicula not particularly sagittate, the wings mostly rather 

 broad, rounded ; branching not markedly divaricate, more or less 



strictly dichotomous or in part pinnate 4 



4. Pinnate branching rare or infrequent below; branch tips 

 usually somewhat attenuated; segments mostly 2.5-3.5 mm. 



broad B. gardnen 



4. Pinnate branching frequent below; branch tips commonly 

 somewhat expanded; segments mostly 3.0-4.0 mm. broad 



B. dichotoma 



5. Thalli more or less abundantly branched above, the ultimate 



branches usually relatively short 6 



5. Thalli sparsely branched above, the ultimate branches mostly 

 long, ligulate, more or less fastigiate ... 5. ligulata 

 6. Main axes mostly percurrent; dichotomous branching rare 

 or infrequent; intergenicula sagittate . . B. sagittata 

 6. Without distinct, percurrent main axes ; dichotomous branch- 

 ing frequent 7 



7. Intergenicula more or less blunt-sagittate, equal or only a little 



broader than long B. cooperi 



7. Intergenicula much broader than long, wing nut shaped . . 

 B. insularis 



Bossea pachyclada Taylor 



Plate 8, fig. 4 



Taylor, 1945, p. 194, pi. 58. Bossea angustata Taylor, 1945, p. 193, 

 pi. 59, Dawson 1951, p. 53. 



Thalli saxicolous, to 10 cm. high, consisting of several to many more 

 or less long-stipitate, dichotomously branched erect parts from a basal 

 crustose stratum ; stipes usually 2-4 cm. long, robust, terete below, with 



