Marine Algce of Berwick-on- Tweed, 375 



73. Fronds gelatinous, but firm, spores in marginal bands or spots. 74 

 Fronds cartilaginous or rigid membranaceous, dense. ... 75 

 Fronds delicate or somewbat coriaceous. ... ... ... 77 



74. Fronds composed of a single layer of cells. . . . Porphyra. 

 Fronds composed of two layers of cells. ... ... Diploderma. 



75. Fronds composed internally of oblong polygonal cells, with a cortical 

 layer of minute, coloured cells, arranged in a vertical series, fronds 

 dark red or purplisb, stipitate, stipes expanding into a rigid mem- 

 branaceous, flat, simple, or cleft lamina proliferous from the disc or 

 margins. ... ... ... ... ••• Phyllophora. 



Fronds cartilaginous, formed internally of a layer of longitudinal 

 slender anastomosing filaments which divide corymbosely at the 

 surface. ... ... •• • ••• ••• 76 



76. Fronds plane or slightly channelled. ... ... Ghondrus. 



Fronds beset with small papilla3,in which the spores are borne. Gigartina. 



77. Midrib present. ... ... ... ... ... 78 



Midrib wanting. ... ... ... ... ... 80 



78. Fronds rose-red, leaf -like. ... ... ... ... 79 



Fronds dark brownish-purple, narrow, dentate,midrib scarcely distinct 

 ... ... ... Odonthalia. 



79. Fronds laciniate or much branched, often proliferous from the midrib, 



cystocarps hemispherical, sessile on the midribs or veins, tetraspores 

 in spots on the frond or sometimes in small lateral leaflets. Delesseria, 

 Fronds bright-red,stalked, stems cylindrical, branched, expanding into 

 oblong, simple leaflets entire at the margins, fruit borne on the old 

 denuded midribs, (in winter), cystocarps spherical, stalked, tetraspores 

 in small special leaflets. ... ... Hydrolapathum. 



80. Fronds narrow much divided. ... ... ... 81 



Fronds palmately or dichotomonsly divided. ... ... 82 



Fronds undivided, dull-red, thick (carnoso-coriaceous) shortly stipitate, 

 stipe compressed, gradually expanding into an obovate, undivided 

 frond, fruit immersed in the frond. ... ... SarcophyllU. 



81. Branches alternately secund in threes or fours, the lowest undivided 

 and spine-like, the upper pectinate on the upper side, tetraspores 

 zonate. ... ... ... ... ... Plocamium. 



Fronds subflabellate, upper divisions divaricately toothed, tetraspores 

 cruciate. ... ... ... ... ... Euthora. 



82. Fronds very thin and delicate. ... ... ... ... 83 



Fronds thickish, snbcartilaginons or submembranaceons. ... 84 



83. Fronds rose-red or purplish, margins entire, usually more or less 



veined, tetraspores cruciate in scattered spots (sori). Nitophyllum. 

 Fronds dark-red, ciliate, tetraspores zonate. Rhodophyllix. 



84. Fronds purplish-red, broadly palmate or dichotomous, sometimes 

 repeatedly laciniate into narrow segments, margins proliferous, 

 tetraspores cruciate in patches. ... ... Pvhodymenia. 



Fronds bright-red, broadly palmate or dichotomonsly divided, margins 

 when in fruit curled and fringed with minute cilia, in which the 

 cystocarps are immersed, tetraspores cruciate in patches. Callophyllix. 



