138 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Fronds pinnate or pinnatifid, compressed or 

 cylindrical, cartilaginous, purple or yellowish 

 tetraspores tripartite, cystocarps external 

 sessile ... ... ... ... ... Laurencia 



Fronds filiform, rigid, irregularly branching 

 forming dense intricate bundles A hnfeltia 



Fronds cylindrical . slightly compressed, cartil- 

 aginous, sparingly and irregularly branching, 

 composed of an inner layer of very large angular 

 colourless cells, and a cortical layer of small 

 coloured cells, tetraspores cruciate, immersed 

 in the frond, cystocarps external sessile Gracilaria 



Fronds small compressed, pinnate, forming small 

 tufts, spores borne on an axial placenta in 

 the enlarged terminal branches ... ... Gelidium 



71. Eoot an expanded disc, spores borne in external 

 flesh-coloured warts, tetraspores cruciate, im- 

 mersed in the frond Poly ides 



Root attached by branching rhizoids, cystocarps 

 and tetraspores immersed in the swollen tufts 

 of the branches, tetraspores zonate Furcellaria 



78. Cystocarps immersed in frond 79 



Cystocarps internal, ovate or urceolate, fronds 



traversed by a distinct central filament ... 82 



79. Fronds gelatinous, composed internally of a 



dense mass of slender longitudinal filaments 

 which give off short corymbose, lateral branches 



which form the cortex 80 



Fronds soft, succulent, consisting of an internal 

 layer of slender longitudinal filaments and a 

 cortex composed of polygonal cells, becoming 

 smaller towards the surface ... Gystoclonium 



80. Cortical filaments throughout the frond free ... 81 

 Cortical filaments of ramuli (only) free, main 



