May, 1906.] Key to Livencorts. 539 



Indeterminately branching; leaves somewhat remote, round-obo- 

 vate; perianth clavate-obconic. Antheridia axillary on 

 short lateral branches, arising near the terminal involucre. 



ohconica Sulliv. 

 Riccia Micheli. 



1. Terrestrial forms growing in rosettes or irregular dichotonious 



forms. Fruit immersed in the upper side of the thallus, 

 mostly protuberant above. Thallus with or without air- 

 cavaties. 2. 

 Aquatic plants floating in water or with its retreat rooting in mud 

 and there fruiting. Fruit immersed in the lower side or the 

 central groove of the thallus. Thallus with air-cavaties. 12. 



2. Thallus mostly without air-cavities. 3. 



Thallus with air-cavaties communicating with the upper surface. 11 



3. Thallus naked, without cilia and scales on the margin and under- 



neath. 4. 

 Thallus with scales underneath, not ciliate or more or less ciliate 

 at the margin and apices. 7. 



4. Spores small (60/t or less). 5. 



Spores larger (75-95/0, dark fuscous with deep reticulations 

 (about 8 across the convex turface); divisioiis of thallus nar- 

 row, arvcnsis Aust. 



5. Thallus with wide divisions, thin and flat, with few rootlets; spores 



muriculate, spinulcse. tenuis Aust. 



Thallus with narrow divisions and numerous rootlets. 6. 



6. Thallus thin, fibrous-reticulate; spores obscurely muriculate. 



Frostii Aust. 

 Thallus canaliculate above, carinate-thick-ened beneath; spores 

 coarsely reticulate. 

 (fluitans, L. var. Snlliva)iti, Aust.) Hucbcncriana Lindenb. 



7. Thallus with scales underneath, not -ciliate. 8. 

 Thallus more or less ciliate at the margin and apices. 10. 



8. Scales and usually the thallus purple underneath; scales not ex- 



ceeding the margin; spores light brown. nigrcUa D. C. 



Scales usually whitish; thallus green underneath. 9. 



9. Scales reaching beyond the margin; spores light brown. 



lamellosa Raddi. 

 Scales not reaching the margin; spores dark brown. 



(sorocarpa Bischoff) minima L. 



10. Capsules usually in a single row; spores blackish, opaque, scarcely 



reticulated {arvoisis Aust. var. Iiirta Aust.) liirta Aust. 



Capsules scattered chiefly near the base of the divisions (with a 

 purple spot near them on the thallus); spores brown, reticu- 

 lated with 7-8 areolae across the convex surface. 



Lcscuriana Aust. 



11. _'Upper surface of thallus strongly pitted, green or reddish to pur- 



plish; divisions of thallus rather broad, obtuse or often obcor- 

 date at the apex. crystallina L. 



Upper surface of thallus mostly smooth (except for the median 

 groove), yellowish green; divisions narrow, linear, obcordate 

 and convex, thickened at the ape.x. liitcscens Schwein. 



12. Thallus linear, dichotonious, floating or rarely terrestrial capsule 



protuberant from the lower surface. fluitans L. 



Thallus obcordate, floating or rarely terrestrial; capsule not pro- 

 truding, at last exposed by a cleft in the central groove. 



natans L. 

 Scapania Dumort. 



1. Lower leaf lobe equalling in size the upper or nearly so. 2. 



Lower leaf lobe (except those near the summit) about twice the 

 size of the upper or 3-4 times its size. 3. 



