NODULARIA. 291 



Genus 96, APHANIZOMENON, Morren. 



Thallus somewhat membranaceous, free swimming, aeruginous 

 or light pure blue, or becoming olive; trichomes medium size, a 

 little attenuated towards the apex, agglutinated parallelly and 

 densely in fascicles ; articulations cylindrical, very closely con- 

 nected, pale blue, nearly colorless, and delicately granular. 

 Spores elongated, cylindrical, rounded at the ends, pale blue or 

 somewhat olive, smooth. Borzi. 



APHANIZOMENON FLOS- AQUAE, Allrnan. 



Fully described by the generic character. 



Diameter of vegetative cells 3.5-5.5 yu; 1-2 times as long 

 as broad ; diameter of spores, 5-5. 5 /<*; 6-12 times longer 

 than the diameter. 



Gathered this species only once ; from a reservoir of rain- 

 water. 



Syn. Limnochlide jtos-aquae, Kg. ; Sphaerozyga flos-aquae, Rab. ; 

 Byss-us flos-aquae, Linn. 



Plate CXCVIII, figs. 7, 8, agglutinated filaments, floating ; 

 figs. 5, 6, specimens of spores. 







Genus 97, NODULAR! A, Mertens. 



Trichomes usually distinctly vagi nate, with closely compressed 

 disc-shaped joints, collected in a gelatinous or membranaceous, 

 irregularly diffused stratum. Heterocysts intercalated at regu- 

 lar intervals; vegetative joints nearly equal, transversely com- 

 pressed. Spores fuscous, or golden yellow, globose, slightly 

 compressed. 



NODULARIA PALUDOSA, Wolle. 



Filaments single or in smaller clusters on marshy grounds ; 

 trichomes nearly straight, of a beautiful aeruginous color ; 

 articulations short, about half as long as wide, granular. 

 Heterocysts nearly globose, yellow. 



Diameter of cells or filaments, 6-8 ^. 



This plant is evidently very closely related to Anabcena\ 

 sometimes it has a sheath, but this appears soon to dissi- 

 pate. Anabcena cupressaphila can scarcely be separated from 

 this Nodularia except that the former has not, usually, the 

 heterocysts at regular intervals; they are distinct also in 

 habitat. These forms are noted merely provisionally. The 

 Nodular iae of Europe occur only in brackish waters and are 



