IJcpafinr of North A))i('r/rti . 27 



IT). R. Donnellii Aust. Diceeiouts; primjiry tluilliis or- 

 Uiciihir. lar^e, often H.S cni. in diameter, substellately divided, 

 nearly i)lane, elegantly and "grossly cristate-reticulate above, 

 pale green both sides; divisions more or less di-trichotomous, 

 often deeply channeled when dry, emarginate at the apex; fruit 

 in a single row, immersed in the midrib; spores very large 

 0.127— ().1<)8 mm. in diameter, subrotund, black, opaque, sub- 

 tuberculate; male thallus usually a little larger; ostioles nu- 

 merous, tiliform, hyaline^ 1 mm. high. 



Hab. — Gardens and cattle-ranges; Fla. (J. Donnell Smith) ■ 



Bib.— Torrey Bull. VI, p. 157. 



§ 2. Spongodes. Thallus tcith large air-cavities and with 

 a slight dejiressiott in the upper surface immediately over the 

 fruit a-hich is prominent on the under surface; upper surface 

 usudlhj broken up into pits communicating with the air-cavities; 

 spores smaller 0.041 — 0.051 mm. in diameter., obtusely angular 

 or globose. Pseudo-aquatic or occurring on wet or muddy 

 ground. 



* Thalli homomorphous, terrestrial. 



16. R. crystallina L. Thallus orbicular, 1 — 2 cm. in 

 diameter; divisions obcordate or cuneate. bifid or bilobed, plane 

 above, the margins subcrenate, the upper surface much- broken 

 up into pits; fruit scattered; spores issuing through the upper 

 surface. {R. plana Tayl., E. relutina Hook, in part.) 



Hab.—^o. States (Drummond, Ravenel), 111. {Hall), Col. (Wolfe), Nev. 

 {Watson). (Eu.) 



Bib.—^yn. Hep. j). 607, Hep. Europ. p. 170. 

 Delhi. — Lindenberg Monog. Ric t. XXII. 



17. R. lutescens Schwein. Thallus light green, orlncu- 

 lar, 2.5 — 3.8 cm. in diameter; divisions — 8, linear, twice or 

 three times forking, narrowly channeled above, obcordate and 

 convex-thickened at the apex, with delicate, whitish, obliquely 

 ovate, appressed scales, and destitute of rootlets above the mid- 

 dle underneath; reproductive organs entirely unknown. 



Hab. — III exsiccated pools and ditches ; Can. to Fla., Mo. and Tex.; 

 common. 



Bib. — Spec. Flor. Amer. Sept. p. 26, Mem. Amer. Acad. n. ser. iv, 

 p. 176, Pro. Phil. Acad. 1869, p. 234. 



Delin. — Mem. Amer. Acad. n. ser. iv, t. IV; Lindenberg Monog. 

 Ric. t. XXVI. 



