246 FRESH-WATER ALG.E OF THE UNITED STATES. 



GLOEOTEICHIA NATANS, Thur. 



Globose or angular, tuberculose, variable in size and 

 form, green, becoming brownish ; trichomes straight, toru- 

 lose, flexuous and hyaline above, lower articulation more or 

 less compressed. Sheath broad, here and there constricted, 

 colorless or yellowish. Spores oblong, cylindrical ; hetero- 

 cysts subglobose. 



N 



Kirchner divides the numerous forms of this species into 

 the following four sections : 



a. TYPICA, (Rivularia Boryana, Kg.). 



Thallus somewhat globose, firm; trichomes with upper 

 part much elongated. Spores cylindrical, 10-13 times as 

 long as thick. 



Diameter of sheath about 36 /*. Spores 11-17 ^. ; hetero- 



cysts, 9-11 /-/. 



b. GIG ANTE A, (Rivularici gigantea, Trent). 



Thallus large, sometimes four or more inches in diameter. 

 ( Had a case reported to me from Maryland, as large as a 

 man's head.) Spores cylindrical, olive, 3-6 times longer 

 than wide. 



Diameter of spores, 9-13 ^ : heteroeysts, 6-8 /*. 



c. ANGTJLOSA, (Itivularia angulosa, Roth). 



Thalli the size of cherries. Spores ellipsoidal, aeruginous- 

 brown, 3-10 times as long as wide. 



Diameter of spores, 14 ^ ; heterocysts, 9-12 yw. 



d. BRAUNIANA, (Eivularia Bmuniana, Kg.). 



Thallus less than cherries in size; trichomes ligulate, 

 sheath narrower than of the preceding. Spores 8-12 times 

 longer than wide. 



Diameter, 10-12 // ; heterocysts. about 9 //. 



Syn. Tremella natanSj Hedwig ; Rivularia gigantea, Trent. ; E. 

 angulosa. Roth ; P. Boryana, Kg. ; R. Brauniana. Kg. , etc. 

 Ponds and stagnant pools. 



Plate CLXXVIII, figs. 15-19, smaller and larger thalli. 

 The larger corresponding with very small specimens of G. 

 gigantea; figs. 4-7, progressive stages of the growth of a 

 trichome; figs. 5, 6, 7, the appearance of the sheath, first 

 simple then constricted; figs. 8-12, progressive stages of 

 another form ; figs. 13, 14, trichomes, fertile and sterile in 

 the same thallus ; fig. 20, a form from Colorado, trichomes 

 peculiarly contorted. 



