THE GREEN ALGAE OF NORTH AMERICA 367 



selves one to another by the thickened tips, forming a more or 

 less spongy frond. 



From Cladophora, Boodlca is distinguished by the adherent 

 tips of the branches, which, however, do not amount to a dis- 

 tinct organ as in Struvea ; from Microdictyon it is distinguished 

 by branching in all directions. 



B. COMPOSITA (Harv. and Hook.) Brand, 1904, p. 187, PI. 

 VI, figs. 28-35; Cladophora composita P. B.-A., No. 722. Form- 

 ing spongy, pale green tufts ; filaments soft, pellucid, dichoto- 

 mous below, above with opposite or whorled branches, all at 

 wide angles; cells 2-5 diam. long; 200-225 /" diam. below, 

 about 1 20 fj. in the ramuli and there not much longer than 

 broad. Fig. 128. British Columbia, Cal. 



Hawaiian and other Pacific Islands. 



This specie's occurs in dense masses in the literal zone ; the 

 cells are much swollen, either ovoid or pyriform, the cell wall 

 thin and delicate. The ramuli are usually opposite, but often 

 whorled, and the habit is much like one of the branching 

 Valonias. 



ii. DICTYOSPHAERIA Decaisne, 1842, p. 32. 



Frond attached by rhizoids, rounded, solid or hollow, con- 

 sisting of a cellular mass, or of a single layer of closely set, 

 polygonal cells, attached to each other by short tenacula ; 

 frond increasing in size by the division of the cells of the single 

 layer, or by externally giving off dense branches, forming an 

 outer layer, the older layer persistent or perishing ; reproduc- 

 tion unknown. 



D. FAVULOSA (Ag.) Decaisne, 1842, p. 32 ; Harvey, 1858, p. 

 50, PI. XUV.B. ; Vickers, 1908, p. 21, PI. XXII; P. B.-A., 

 No. 124. Frond always hollow, hemispherical or oblong in 

 shape, unless broken by external causes; cells 5-6-angled, up 

 to 2 mm. diam. Fig. 137. Fla., W. I., Mexico. 



Indian and Pacific Oceans. 



The roundish, light green, berry-like fronds, from 2 to 10 cm. 

 diam., grow attached to corals and rocks, and are not likely to be 

 mistaken for anything else. 



12. HORMISCIA Fries, 1835, p. 327. 



Filaments simple, attached at the base by growths from 

 within the cell, or from the cell wall ; cells multinucleate, all 

 above the base similar, capable of division and of producing 

 zoospores ; chromatophore covering the cell wall, entire or net- 



