THE MARINE ALG.E OF NEW ENGLAND. 191 



73. Fronds long, cylindrical, densely clothed with lake-red hairs . . Dasya. 

 Fronds purple or dark red, occasionally blackish, superficial cells 



either throughout or at least in the young branches arranged in 



transverse bands , 74 



Fronds dark red, much branched, rather robust, superficial cells 

 small, irregularly placed Mhodomela. 



74. Tetraspores borne in the younger branches Polysiphonia. 



Tetraspores borne in swollen, pod-like branches (stichidia). 



Bostrychia. 



75. Fronds cartilaginous, dense, spores immersed in the substance of 



frond 76 



Fronds delicate or somewhat coriaceous 79 



Fronds gelatinous, livid purple, composed of a single layer of cells, 



spores in marginal bands or spots Porphyra. 



76. Fronds formed internally of numerous anastomosnig filaments which 



divide corymbosely at the surface 77 



Fronds formed of roundish angular cells throughout 78 



77. Fronds plane or slightly channelled Chondrus. 



Fronds beset with small papillae, in which the spores are borne. 



Gigartina. 



78. Fronds with a prominent stipe, which passes into a proliferous la- 



mina, cystocarps external, globose .... Phyllophora. 



Fronds linear, regularly dichotomous, cystocarps immersed. 



Gymnogongrus. 



79. Midrib present 80 



Midrib wanting 82 



80. Fronds rosy red, leaf-like 81 



Fronds dark brownish purple, narrow, dentate, midrib scarcely dis- 

 tinct „ Odonthalia. 



81. Tetraspores in spots on the fronds, lateral veins usually present. 



Delesseria. 



Lateral veins wanting, tetraspores in thickened portions of the 



fronds ... . - Grinnellia. 



82. Fronds narrow, much divided 84 



Fronds palraately or dichotomously divided 83 



83. Fronds deep red, broadly palmate, margins proliferous, tetraspores 



cruciate in patches Bliodymenia. 



Fronds dark red, margins ciliate, tetraspores zonate . . Rhodophyllis. 

 Fronds dark i^urple, deeply divided, tetraspores scattered, cruciate. 



Gracilaria. 



84. Branches alternately secund in threes or fours, the lowest undivided 



and spine-like, the rest pinnate Plocamium. 



Fronds subflabellate, upper divisions divaricately toothed. UutJiora, 



