90 University of California Pulilications in Botany [Vol. s 



The family of the Nostoeaceae is thoroughly distinct and its mem- 

 bers easil}^ recognizable. Naegeli used the term in an extended sense. 

 Bornet and Flahault also used it in an extended sense in their title 

 but their tribe Nostoceae (1887, p. 177) has the same limits as has 

 gradually come to be customarj^ and as we shall use it. 



Most of the Nostoeaceae are inhabitants of the fresh waters, but 

 a few are marine or brackish water species. Only two species of this 

 family have been detected on this coast and one of these is not strictly 

 a marine or brackish water species. Probably several species remain 

 to be detected. 



Key to the Genera. 



1. Trichomes contorted and twisted, united into a definite gelatinous thallus 



24. Nostoc (p 92) 



1. Trichomes straight, united into indefinite gelatinous masses 



23. Anabaena (p 90) 



23. Anabaena Bory 



Trichomes cylindrical or slightly tapering at the ends, without a 

 sheath, or in some species with a thin mucous tegument, existing 

 apart or united loosely by the mucous teguments into a stratum ; 

 heterocysts intercalary; spores single or seriate, spherical to cylin- 

 drical. 



Bory, Diet. Class, d'hist. nat., vol. 1, 1822, p. 307. 



Bory in 1822 established the genus Anahaena {" Anahaitia") on five 

 species: of which one, viz., A. oscillorioides Bory, remains to represent 

 two of them ; one species is uncertain ; one is Phorniidium laminosiim 

 (Ag.) Gomont, and the fifth is referred to " Leptothrix lamellosa 

 Kuetz. ' ' The type of the genus is Anabaena oscillariaides Bory. The 

 original spelling of the genus was " Anahaina," changed later into 

 "Anabaena" to accord with usage in transliterating from Greek into 

 Latin, the earlier diphthong ai becoming in classical Latin ae. 



Key to the Species. 



1. Trichomes 2.6-3/a in diam., spore wall hyaline 1. A. propinqua (p 90) 



1. Trichomes 4-6/* in diam., spore wall brown 2. A. variabilis (p 91) 



1. Anabaena propinqua S. and G. 



Plate 8, fig. 9 



Stratum very thin, light blue-green ; trichomes flexuous, 2.6-3ju. 

 diam. witliout a distinct sheath ; cells subquadrate, 1.8-3ju. long, cylin- 



