MARINE AI<GM OF BEAUFORT, N. C. 535 



ff. Frond with ultimate branchlets club shaped and terminated by brushlike tufts of 



hairs, no floats present SPOROCHNUS (p. 448). 



aaaa. Frond terete throughout, variously branched g. 



g. Frond forming a hollow tube, constricted and twisted at irregular intervals, about 



2 mm. in diameter, dichotomously branched ROSENVINGEA (p. 443). 



gg. Frond not conspicuously tubular, about i mm. in diameter, irregularly branched, 



spongy texture CASTAGNEA (p. 446). 



ggg. Frond solid or nearly so, less than i mm. in diameter, dichotomously -, 



branched '. STILOPHORA (p. 448)? 



aaaaa. Frond more or less flattened, simple or branched h. 



h. Frond consisting of one or more elongated, leaflike lobes PETALONIA (p. 443). 



hh. Frond fan shaped throughout or at least in the terminal segments . 



*. Frond or segments bearing concentric zones parallel with the apical margins, apical 



margins inrolled PADINA (p. 455). 



it. Frond or segments bearing radial markings running from the base to the apical 



margins, apical margins not inrolled ZONARIA (p. 454). 



hhh. Frond dichotomously branched j. 



j. Frond tough, leathery, usually with bladderlike floats at intervals in frond 



Fucus (p. 450). 



jj. Frond membranaceous, no floats present k. 



k. Distinct midrib present DICTYOPTERIS (p. 459). 



kk. No midrib present /. 



/. Frond growing in length by group of initial cells, edges more or less serrate or 



dentate SPATOGLOSSUM (p. 458). 



//. Frond growing in length by single apical cell, edges with occasional prolifer- 

 ations but not serrate or dentate DICTYOTA (p. 460). 



AAAA. Color various shades of red, pink, purple, sometimes blackish, yellowish, or green 

 (if green, structure apparently cellular, not entirely composed of interwoven 

 filaments), sometimes white from incrustations of lime; filamentous or forming 

 sheets or complex structures of various shapes; some forms epiphytic, some minute, 



parasitic on other algae; usually attached IV. RHODOPHYCE^. 



o. Frond not incrusted with lime 6. 



6. Frondminute, parasitic, formingswollenknotson6 : pwo9on9r^9nJ^^t.AcTiNOCOCCUS(p. 477). 



66. Frond filamentous c. 



c. Filaments creeping, closely adherent, forming irregular patches . ERYTHROCLADIA (p. 466). 



cc. Filaments more or less erect d. 



d. Filaments regularly dichotomous, tips usually incurved CERAMIUM (p. 513). 



dd. Filaments not regularly dichotomous e. 



e. Filaments consisting throughout, or for the most part, of a single rt>w of cells; 



simple or branched /. 



Y. Filaments sparse, scattered or few occurring in small tufts on other algse; 

 almost microscopic in size; slight branching by method known as "false 



branching" GONIOTRICHUM (p. 465). 



ff. Filaments composed of obovate or barrel-shaped cells GRIFFITHSIA (p. 511). 



fff. Filaments densely branched, forming erect, fairly conspicuous tufts on rocks 



or plants CAUJTHAMNION (p. 511). 



ffff. Filaments growing in hydroids Acrochcetium infestans (p. 473). 



fffff. Filaments forming more or less dense mats over other algae g. 



g. Mat very fine, velvety, often inconspicuous except for the reddish tinge 



given the host; filaments minute ACROCILETIUM (p. 469). 



gg. Mat coarser, conspicuous * 



h. Individual filaments easily discembile, rather coarse; mat dark red, 



rather loose ERYTHROTRICHIA (p. 466). 



hh. Individual filaments scarcely discernible, rather fine, velvety; mat 



bright red, dense SPERMOTHAMNION (p. 510). 



