136 TBANSACTIONS LIVEKPOOL BIOLOGICAL SOCIETY. 



Fronds composed of a single row of cells above, 

 but below with a false cortex formed by the 

 growth of descending filaments given off from 

 the cells 72 



Fronds formed of large cells placed end on end, 

 with bands of smaller cells at the nodes, in 

 some cases the nodal cells extending in a thin 

 layer over the internodal cells 73 



67. Spores on short pedicels distinct undivided .. 68 

 "^ronds composed of prostrate, creeping filaments 



from which arise erect, dichotomous or irregu- 

 larly branched filaments ... ... Rliodochorton 



Both tetraspores and cystocarps present 69 



68. Spores terminating short lateral brajiichesChantransia 

 Spores axillary Monospora 



69. Cystocarps terminal, involucrate, spores irregu- 



larly grouped not surrounded by a common 

 gelatinous envelope when mature ... ... 70 



C ystocarps terminal or lateral, spores irregularly 

 grouped at maturity, covered by a general 

 gelatinous envelope 71 



70. Fronds formed of prostrate filaments from 



which arise erect pinnate filaments Spe?'mothamnion 

 Fronds pinnate, ramuli whorled Spliondylothamnion 



71. Fronds dichotomous formed of delicate vesicular 



cells, tetraspores in involucrate whorls at the 

 nodes or on the inner side of short fascicled 

 branches Griffiths ia 



Fronds dichotomous or pinnate, branches alter- 

 nate, tetraspores tripartite, favellae binate, 

 lateral Gallithamnion (in part) 



Fronds pinnate, favellee terminal, involucrate ; 

 tetraspores polysporic Pleonosporium 



