NO. 8 DAWSON : A REVIEW OF THE GENUS RHODYMENIA 125 



Of the 54 species listed here, 27 have been studied from actual, pre- 

 served material. The rest are interpreted from the literature, but it is 

 hoped that additional, authentic specimens may be available as the work 

 on this genus continues. 



KEY TO THE SPECIES OF RHODYMENIA 



A. Plants sessile, or with unbranched stipes, or with only stoloniferous 

 branching from the base subgenus Eurhodymenia 



I. Tetraspores never in son, dispersed over surface of frond in un- 

 modified cortical layer Sec. 1. PERTUSAE 



Frond simple or branched from near base of stipe, without 

 marginal proliferations; blade undivided or with few, ir- 

 regular, broad lobes 



Frond up to 60 cm. high, perforated, 150-200 [x thick; 



type: — Kamchatka R. pertusa 



Frond up to 25 cm. high, unperfo rated, 250-300 \\. thick; 



type: — Washington R. stipitata 



Frond dichotomously divided into more or less cuneate seg- 

 ments 



Apex of the segments rather broad, blunt, notched ; mar- 

 gins entire 



Fronds gelatinous, adhering to paper; type: — Peru 



R. peruviana 



Fronds not gelatinous ; type : — Japan . R. cuneifolia 

 Apex of segments attenuated ; margins entire or foliifer- 



ous; type: — New Zealand R. sanguinea 



(R. lanceolata) 

 Of doubtful affinity ; apex of segm.ents often multifid ; 

 fronds coriaceous; margins entire, denticulate, or pro- 

 liferating; type: — Red Sea R. erythraea 



II. Tetraspores in irregularly shaped sori, often slightly raised and 



in cross section showing modification of the cortical layers to 



produce a nemathecioid structure . . Sec. 2. PALMATAE 



Fronds dichotomous, not showing a palmatifid branching 



form 



Tetraspores in vermicular sori ; margins entire or pro- 

 liferous; type: — Borneo R. indica 



Tetraspores arranged in broadly anastomosing, hiero- 



