216 



ALG^E 



mentary alternation of generations ; and Peter asserts (Bot. Verein 

 Miinchen, Feb. 28, 1887) that the sexual form of Lemanea fluviatilis (Ag.) 

 may develop out of heteromorphic branches of a Chantransia. 



LITERATURE. 



Wartmann Beitr. zur Anat. und Entwick. der Lemanea, 1854. 



Sirodot Ann. Sc. Nat., xvi., 1872, p. 5; 1873, p. 241 ; and Compt. Rend., Ixxix., 



1874, p. 1366. 

 Ketel Anat. Untersuch. iiber Lemanea, 1887. 



The PORPHYRACE^E or Bangiaceaa are marine or fresh-water Algae 

 belonging to the two genera Porphyra (Ag.) and Bangia (Lyngb.). They 

 are regarded by some authors as much lower in structure than the red 



FIG. 194. B.fnsco-purpurea Lyngb. Filament 

 in different stages of development (-X 200). 

 (After Kiitzing.) 

 FIG. 193. -a, b, Bangia ceramicola 

 Chauv. Portions of barren and fertile 

 filaments (x 330). (After Thuret.) 



seaweeds, but are best placed at present, from their mode of sexual 

 reproduction, as one of the lowest families of Florideae. The thallus is 

 either filiform (Bangia), or is a thin transparent plate (Porphyra) com- 



