llcpaticce of North America. 31 



ORDER II. MARCHANTIACE^B CORDA. 



Terrestrial (rarely amphibious), usually perennial plants 

 with thallose vegetation. Thallus dichotomously, subpalmately 

 or radiately branched, usually continuous or proliferous from 

 the apex of the midrib or from its side underneath, more or less 

 thickened in the middle, furnished beneath with numerous long 

 rootlets, and usually colored and imbricating scales (root-like 

 hairs in Dumortiera). Epidermis more or less distinct, usually 

 porose. Capsules globose, rarely obovate or oval, attached to 

 the underside of disk-like receptacles which are elevated on 

 peduncles (in a bivalved receptacle underneath the apex of the 

 thallus in Targionia), opening variously or indehiscent. Ela- 

 ters usually present, mixed with the spores. 



ARTIFICIAL SYNOPSIS OF GENERA 



Fruit aggregated underneath large, peduncled recepta- 

 cles B 



Fruit sessile under the apex of the thallus which is 

 small with conspicuous pores. XIII. TARGIONIA. 



B 



Inner involucre present .' C 



Inner involucre wanting E 



Inner involucre conspicuous, split into 8-16 pendent, 

 linear divisions. X. FIMBRIARIA. 



Inner involucre 4-5 lobed D 



f Carpocephalum 7-9 rayed. I. MARCHAKTIA. 



) Carpocephalum hemispheric, 1-4 lobed, with as many 

 rib-like rays. II. PREISSIA. 



f Outer involucre present F 



| Outer involucre wanting; thallus obcordate, barely cos- 

 1^ tate, eporose. VI. CRYPTOMITRIUM. 



Carpocephalum entire at margin or nearly so G 



F 



Carpocephalum lobed, cleft or divided H 



