1920] Setchell-Gardner : Chlorophyceae 177 



face of segments and producing 2-ciliated zoospores ( ?) whose further 

 development has not been followed. 



Lamouroux, Class. Polypes, 1812, p. 186. 



The genus Ilalimeda is very well marked on account of its calcified, 

 jointed structure, most of the species are strongly calcified, but in the 

 single species thus far detected on our coast the calcification is slight. 

 The species are strictlj' tropical, occurring in abundance on coral reefs 

 and assisting materially in their formation. Otto Kuntze (1891, p. 

 908) has urged the substitution of the earlier name Opuntiodcs of 

 Ludwig (1737, pi. 138), but since HaUmeda has been in practically 

 undisputed use for over a century, it seems best to retain it as a 

 "nomcn conservandum" if necessary. 



Halimeda discoidea Dec'ne 

 Plate 13, fig. 3 



Fronds branched in one plane, up to 15 cm. high, nearly orbicular 

 in outline, very slightly calcified, color bright green, fading on drying ; 

 segments mostly quadrangular-oblong or cuneate-obovoid, the longer 

 axis longitudinal rather than transverse, thin, smooth ; central fila- 

 ments fused in twos, rarely threes, at the nodes; utricles of subcortical 

 layer 68-175/a diam., larger than the interlocked, often fused, peri- 

 pheral utricles. 



La Paz, Lower California. 



Deeaisne, Mem. sur Corall., 1842a, p. 102; Howe, Phyc. Studies 

 III, 1907. pp. 495-500, pi. 25, f. 11-20, pi. 26, Phyc. Studies V, 1911, 

 p. 492. 



Only a single species of Halimeda has as yet been credited to our 

 coast and from a single locality, viz.. La Paz in California Baja (or 

 Lower California), Mexico. From this locality it is reported by Plowe 

 {loc. cit.), and we have also specimens collected at the same locality 

 by Dr. and Mrs. Marchant. It is to be distinguished fairly readily 

 from other flat, jointed species by its slight calcification and by the 

 large rounded utricles of the subcortical layer. Other species are to 

 be looked for along the tropical portion of our coast. 



FAMILY 7. VAUCHERIACEAE dumort. 



Filaments simple or usually more or less dichotomously branched, 



cylindrical throughout or witli frequent constrictions, without septa, 



often gregarious into expanded tufted oi- feltlike masses, attached at 



first by colorless rhizoidal branches; chromatophores numerous, small. 



