HE VISED LIST OE MARINE ALG.E. • 137 



Brandies opposite or whorled, tetraspores cru- 

 ciate ... ... ... ... ... Antithamnion 



Fronds with a monosiphonous axis, partly con- 

 cealed by the densely whorled branches, 

 cystocarps terminal on short branches, tetra- 

 spores in whorls one above another on special 

 branches ... ... ... ... ... Halurus 



72. Fronds capillary or bushy, densely branching, 



cortications confined to the larger branches, 

 and evidently formed of vein-like descending 



filaments Callithamnion (in part) 



Fronds compressed,ancipital,branches,pectinate- 

 pinnate, covered everywhere, except at the tips, 

 by polygonal areolated cells ... ... ... 74 



73. Fronds dichotomous, tips usually incurved Ceramium 

 Fronds pinnate, main branches corticated 



throughout with cells arranged in transverse 

 bands, secondary branches corticated only at 

 the nodes ... ... ... ... ... Spyj'idia 



14:. Opposite pinnae of equal size, cystocarps J tC]> 

 minal on the branches, tetraspores solitary 

 on the ends of the branches ... ... Plumaria 



Pinnae of unequal sizes, one being short and 

 simple the opposing one comparatively long 

 and pinnately divided or compound, cysto- 

 carps on special short pinnae or on the upper 

 margins of the ultimate branches, tetraspores 

 clustered ... ... ... Ptilota 



75. Fronds dark-red or nearly black, substance dense 76 

 Fronds rose-red or purple, rather succulent or 



gelatinous, sometimes capillary ... ... ... 78 



76. Fronds compressed, fringed with minute ramuli, 



cystocarps terminal on the ramuli Sphcerococcus 

 Fronds dichotomous, cylindrical", cartilaginous 77 



