164 SAUNDERS [4] 



The plant forms minute, hard, dark bluish green thalli 1-3 mm. in 

 diameter, which finally become agglutinated into hollow indefinite 

 masses. 



Family HTDR URA CE^ft. 



Hydrurus penicillatus Ag. 



Plant forming dark olive-green filaments attached to smooth round 

 pebbles in a rapid brook emptying into Kukak Bay (351). 



The filaments are 7-20 mm. in length, having long primary branches 

 bearing many short penicill-ate ones. 



CONJUGATE. 

 Family DESMIDIACE^. 



Mesotaenium braunii De Bary. (Plate XLIII, fig. 29.) 



In a freshwater pond near Cook Inlet. 



The cells are cylindrical, 2^ times as long as broad; 16 to iS/z 

 broad, 38-45 <j. long. 



Penium interruptum Breb. 



In a freshwater pond near Seldovia, Cook Inlet. 



Plant 24-40 /./ wide, 130-145 ,u long. Slightly smaller in all its di- 

 mensions but agrees otherwise with the description. 



Penium closterioides Ralfs. 



In a freshwater pond on Popof Island. 

 Diameter 140^, length 150^.. 



Penium margaritaceum (Ehrenb.) Breb. 

 Occasional in freshwater, Kukak Bay. 

 Cells 25 {j. wide, 100 IJL long. 



Penium polymorphum Perty. 

 In quiet water near Kukak Bay. 

 Cells 22 fj. wide, 35 /j. long. Very delicately punctate-striate. 



Penium oblongum De Bary. 



In a freshwater pond near Virgin Bay, Prince William Sound 



Diameter 21 /*, length 64^. 



Penium digitus (Ehrenb.) Breb. (Plate XLIV, fig. 3.) 

 In quiet water, Virgin Bay. Rare. 

 Diameter 54 /a, length 183/4. The plant averages almost a third 



