210 University of California Puhlications in Botany [Vol.8 



CladopJwra hcmisphuerica is another species of the AcgagropUa 

 section, found thus far in a single locality, but growing on rocks where 

 the small indentations retain water at the upper limits of the littoral 

 belt. The filaments are bound together at the base by descending 

 rooting branehlets but are entangled above. Tufts growing in deeper 

 pools sometimes give rise to more slender and looser erect tufts more 

 like individual plants of the Eucl-adophora section. 



Cladopliora heniisphaerica resembles somewhat C. trichotoma, as 

 found on our coasts, but is more distinctly tufted, of different aspect 

 and with more slender filaments. It is attached very firmly to the 

 wave-swept rocks. 



3. Cladophora trichotoma (Ag.) Kuetz. 

 Plate 16, fig. 2 



Plants forming light or bright green, densely pulvinate masses, 

 2-5 cm. high in shallow pools, and up to 2.5 dm. in deep, quiet pools ; 

 filaments procumbent at the base, stiff, di-trichotomous, with rather 

 few, short, alternate, rarely opposite branches, fastigiate at the tips; 

 segments 120-250jli diam., 4-10 diam. long, nearly cylindrical below, 

 above ovoid to pyriform; the branches about the same diameter as 

 the filament. 



Growing in rock pools near high water mark. Vancouver Island, 

 British Columbia, to La Paz, Lower California. 



Kuetzing, Sp. Alg., 1849, p. 414; Collins, Green Alg. N. A., 1909, 

 p. 349 ; Howe, Phyc. Studies V, 1911, p. 492 ; Collins, Holden and 

 Setchell, Phyc. Bor.-Amer. (Exsicc), no. 820. Conferva trichotoma 

 Agardh, Syst., 1824, p. 121. Cladophora repens Collins, Holden and 

 Setchell, Phyc. Bor.-Amer. (Exsicc), no. 727 (not of Harvey). 

 Cladophora columhiana Collins, in Setchell and Gardner, Alg. N.W. 

 Amer., 1903, p. 226. Cladophora composita Setchell and Gardner, 

 Alg. N.W. Amer., 1903, p. 226, as to "N. L. G. no. 521." Cladophora 

 cartilaginea Tilden, Amer. Alg. (Exsicc), no. 376. 



Cladophora trichotoma is the most common of all our species of 

 Cladophora and is usually abundant on all rocky shores from Van- 

 couver Island to La Paz in Lower California. It grows high up on 

 the bare rocks or in small pools where its compact bright green 

 cushions or expanded tufts form conspicuous objects. Our plant has 

 been compared with a fragment of the type specimens and agrees so 

 closely as to be referred here with considerable confidence. Its exten- 



