398 
PACIFIC SCIENCE, Vol. VIII, October, 1954 
BROWN ALGAE 
Key to the Genera of Phaeophyta 
1. Thallus crustose 2 
Thallus not crustose 4 
2. Crust loosely attached, partially free. . . . 
Pocockiella 
Crust firmly adherent to rock surface 
throughout 3 
3. Thallus lubricous, consisting of erect fil- 
aments of + — catenate cells, readily 
separating under slight pressure 
Mesospora 
Thallus not particularly lubricous; cells 
not catenate; filaments not separating 
easily Ralfsia 
4. Thallus delicate, consisting of branched 
filaments less than 100 ^ in diameter. . 5 
Thallus more massive, not consisting 
of branched filaments 6 
5. Filaments uniseriate, attenuated, without 
large terminal cells Ectocarpus 
Filaments with both transverse and ver- 
tical walls; with large terminal cells. . . . 
Sphacelaria 
6. Thallus reticulate Hydroclathrus 
Thallus not reticulate 7 
7. Thallus hollow, bullate or tubular 8 
Thallus solid 9 
8. Thallus branched Rosenvingea 
Thallus unbranched, smooth, papillate or 
lobed Colpomenia 
9. Thallus thin, membranous throughout. 
10 
Thallus with terete axes 11 
10. Thallus fan-shaped Padina 
Thallus dichotomously branched 
.Dictyota 
11. Branches terete, similar to the axes. . . . 
Chnoospora 
Branches of specialized form 12 
12. Ultimate branchlets consisting of leaf- 
like blades and hollow vesicles 
Sargassum 
Ultimate branchlets coarse, obconical . . 
Turbinaria 
Key to the Species of Ectocarpus 
1. Plurilocular sporangia short, pyriform. . . 
E. breviarticulatus 
Plurilocular sporangia elongate. ...... .2 
2. Plurilocular sporangia with acute tips. . . 
E. irregularis 
Plurilocular sporangia with blunt tips . . . 
E. mitchellae 
Ectocarpus breviarticulatus J. Agardh 1847: 
7 (Pacific southern Mexico) ; B0rgesen 
1914: 17, fig. lOa-d; Setchell 1924: 171, 
fig. 37 
Fig. I4a, h 
LOCAL DISTRIBUTION: Dominant with 
Chnoospora pacipca on rocks, Sta. 8 (11263). 
An epiphytic form also occurs on the Chnoos- 
pora (11271). 
This species is characterized by the presence 
of numerous hooked branchlets which hold 
the filaments in rope-like, spongy strands. The 
short, pyriform sporangia, about 40 fx long, 
are also distinctive. 
Ectocarpus irregularis Kiitzing 1845: 234 
(Adriatic Sea); Kiitzing Tab. Phyc. 5, pi. 
62, fig. 1; Bprgesen 1941: 23, figs. 8-11 
(extensive synonymy) 
Fig. 14^, / 
LOCAL DISTRIBUTION: Growing in soft tufts 
to 1.5 cm. high on non-coral rocks, Sta. 2 
