140 TBANSACTIONS LlVEBPOOL BIOLOGICAL SOCIETY. 



84. Fronds brown-red (turning bright red in fading) 



main stems corticated with irregularly shaped 

 cells, densely clothed with bright red hairs, 

 young branches naked, tetraspores in swollen 



pod-like branches (stichidia) Dasya 



Fronds purple or dark-red, tetraspores borne in 

 young branches Polysiphonia 



85. Fronds gelatinous but firm 86 



Fronds cartilaginous or rigid, sometimes dense 87 

 Fronds delicate or somewhat coriaceous ... 90 



86. Fronds purplish, composed of a single layer of 



cells, spores in marginal bands or spots Porphyra 

 Fronds rose-red, composed of a double layer of 

 cells connected by a loose network of colour- 

 less anastomosing filaments, spores attached to 

 the inner surface of the membrane Halymenia 



87. Fronds formed internally of numerous anasto- 



mosing filaments which divide corymbosely 



at the surface 88 



Fronds formed of roundish angular cells throughout 90 



88. Fronds plain or slightly channelled . . . Chondrus 

 Fronds beset with small papillae in which the 



spores are borne Gigartina 



89. Fronds with a more or less evident stipe which 



passes into a proliferous lamina, cystocarps 



external Phyllophora 



Fronds linear, regularly dichotomous, cystocarps 

 immersed Gymnogongrus 



90. Midrib present 91 



Midrib wanting 92 



91. Fronds rose-red, leaf-like ... ... ... Delesseria 



Fronds dark brownish purple, narrow, dentate, 



midrib scarcely distinct Odonthalia 



