162 MIDDLESEX FLORA. 



Penium, De Bar. 



P. minutum, Cleve. 



P. margaritaceum, Breb., var. punctulatum, Ralfs. 



P. Digitus, Breb. 



Closterium, Nitzsch. 



C. acerosum, Ehren. 

 C. costatum, Corda. 

 C. angustatum, Kuetz. 

 C. juncidum, Ralfs. 



NOSTOCACEyE. 



Calothrix, Thuret. 



C. confervicola, Ag. 



Medford and Everett, on Ulva, etc., in salt water. 

 C. Crustacea, Thuret. 

 With the preceding. 



Mastigonema, Kirchner. 



M. aerugineum, Kirchner. 

 Billerica, on Batrachosperinum, (E. Faxon"). 



RivULARiA, Roth. 



R. radians, Thuret. 

 Spot Pond, Stoneham. 



Gloiotrichia, Ag. 



G. pisum, Thuret. 

 Medford and Newton (W. G. Farlow). 



SCYTONEMA, Ag. 



S. ambiguum, Kuetz. 



Newton (W. G. Farlow). 

 S. Hoffmann!, Ag. 



Newton (W. G. Farlow). 

 S. Guyanense, Mont. 

 Newton, in a greenhouse, (W. G. Farlow). 



TOLYPOTHRix, Kuetz. 



T. /Egagropila, Kuetz. 



Spot Pond, Stoneham. 

 T. truncicola, Thuret. 



Newton (W. G. Farlow). 



