400 University of California Puhlications in Boiamy [Vol. 8 



7. Fronds monosiphonous 2. Ectocarpaceae (p. 400) 



7. Fronds more complex 8 



8. Growth trichothallic 9 



8. Growth subterminal, not distincth^ trichothallic 10 



9. Sori distinct, more or less transversely arranged, superficial or projecting.... 



9. Striariaceae (p. 528) 



9. Without distinct sori, sporangia and gametangia neither superficial nor project- 

 ing 11. .ffigiraceae fp. 543) 



10. Fronds dichotomousty much branched 13. Chnoosporaceae (p. 552) 



10. Fronds alternately branched on all sides 



12. Heterochordariaceae (p. 549) 



FAMILY 2. ECTOCAEPACEAE harvey 



Thallns of monosiphonous filaments, occasionally partially poly- 

 siphonous, branched in various ways, arising from creeping, superficial 

 or at times penetrating filaments, occasionally arising from a small 

 superficial disk, usually entirely free from one another, occasionally 

 slightly intertwined or loosely united by a thin jelly ; growth proceed- 

 ing from a subapical cell, often situated at the base of a hair (tricho- 

 thallic) ; cells uninucleate with one or more parietal chromatophores 

 of fixed and definite form ; zoosporangia unilocular, terminal, either a 

 branchlet transformed wholly or in part, or intercalary ; gametangia 

 plurilocular, of various shapes, arising from a branchlet transformed 

 wholly or in part, or intercalary, in some cases differentiated as to 

 size and number of divisions (mega- and meio-gametangia) ; game- 

 tophyte and sporophyte identical in size and structure. 



Ectocarpaceae Harvey, Ner. Bor.-Amer., part 1, 1852, p. 132 (in 



part) ; Kjellman, in Engler and Prantl, Die natiirl. Pflanzenfam. Teil 



1, Abt. 2 (Lief. 60), 1891, p. 182 (in part) ; Oltmanns, Morph. und 



Biol, der Algen, vol. 2, 1922, p. 6 (in part). Ectocarpeae Agardh, 



Syst. Alg., 1824, p. XXX (in part) ; Oltmanns, Morph. und Biol, der 



Algen, vol. 1, 1904, p. 353 (in part). Kuetzing, Phyc. Gen., 1843, 



p. 287 (in part) ; Oltmanns, Morph. und Biol, der Algen, vol. 1. 1904, 



p. 353 (in part). 



Key to the Genera 



1. Zoosporangia and gametangia transformed branchlets or tips of branches or 



branchlets, strictly terminal 2 



1. Zoo.sporangia and gametangia catenate, intercalary 3. Pylaiella (p. 401) 



2. Vegetative filaments superficial or penetrating the host merely by 



rhizoids 4. Ectocarpus (p. 407) 



2. Vegetative filaments deeply penetrating the host, projecting little, if 

 at all, beyond its surface 5. Streblonema (p. 440) 



