28 Illinois State Laboratory of Natural History. ' 



18. R. tenuis Aust. Thallus thin, olive or yellowish 

 green, shining; divisions 2 or 4, expanded, roundish-obovate, 

 plane, 4 8 mm. long, the margins sinuate; beneath green, 

 narrowly carinate by a slender costa, with a few delicate root- 

 lets; fruit in the nerve; capsule extremely delicate, closely ad- 

 hering to the substance of the thallus, crowned with a minute 

 oblong style; spores round or short oval with a conspicuous de- 

 pression in one end when dry, bursting through neither surface 

 of the thallus. 



Hob. Wet broken ground in open woods. Closter, N. J. (Austin), 

 near Lawrence, N. J. (James), Mo. (Hall). 

 Sib. Pro. Phil. Acad. 1869, p. 233. 

 Essie. Hep. Bor.-Amer. No. 150. 

 ** Thalli dimorphous or polymorphous, pseudo-aquatic. 



19. R. fluitans L. Thallus thin, green, orbicular, radi- 

 ately expanding, 2.5 5 cm. in diameter, floating, often form- 

 ing extensive patches ; divisions often much imbricated or some- 

 what entangled, narrowly linear, usually 1 1.5 mm. wide, re- 

 peatedly forking, fibrous-nerved in parallel lines, plane above, 

 convex and eradiculose beneath, cavernous only toward the 

 apex; apices slightly dilated, very obtuse or subtruncate, emar- 

 ginate ; fruit present only in some terrestial forms, very prom- 

 inent below, at length rupturing beneath the thallus. (Ricci- 

 ella fluitans Al. Braun.) - Forma LATA has a broader 

 thallus and a minute patch of fuscous purple, triangular scales 

 at the extremities of the divisions underneath; sterile. 

 Forma NODOSA (R. nodosa Bouch. ) has the thallus here and 

 there tuberously thickened ; sterile. - Forma CANALICULATA 

 (R. canaliculata Hoffm.) is small, pale, terrestrial from drying 

 up of waters on which it floated ; divisions narrower and thick- 

 er, more or less channeled above, radiculose beneath; rarely 

 fertile. Forma TEEEESTEIS is darker green with divisions 

 shorter and slightly depressed-canaliculate above; usually fer- 

 tile. Passes through the above forms to 



Far. Sullivanti Aust. Thallus orbicular ; radiately much 

 divided, cellular-succulent, shining, yellowish green, 0.6 1.7 

 cm. in diameter; divisions twice or three times forked, linear, 

 about 1 mm. wide, straight, canaliculate above, carinate thick- 



