JUNGERMANNIACEAE. 



505 



longitudinal ranks, two dorsal or lateral and one ventral, those of the 

 ventral rank (the underleaves) smaller than t lie others and sometimes 

 absent altogether. Antheridia borne singly or in some groups in the axils 

 of more or less specialized leaves, the perigonial bracts. Archegonia borne 

 singly or in groups at the tips of branches, surrounded by specialized 

 leaves, the perichaetial bracts and bracteoles. Perianth present in many 

 genera, consisting of a cylindrical or prismatic tube open at the apex. Cap- 

 sule spherical to cylindrical. About 150 genera and some 4,000 species, 

 widely distributed, most abundant in tropical regions. 



A. Leaves undivided but often toothed. 



B. Leaves bilobed and complicate, the ventral lobe, or lobule, 



smaller than the dorsal and usually specialized as an 

 inflated water-sac. 



1. Underleaves none. 



Plants large, perianth with a broad truncate mouth. 

 Plants minute, perianth abruptly contracted to a 

 small tubular mouth. 



2. Underleaves present, one for every lateral leaf. 



3. Underleaves present, one for every two lateral leaves. 



a. Lobule inflated but not helmet-shaped, attached to 



the dorsal lobe by a long keel. 

 * Underleaves bifid. 



t Plants pale green to yellowish green. 



Divisions of underleaves not subulate. 

 Perianth inflated, more or less distinctly 

 five-keeled. 

 Lobule with a hyaline papilla at the 

 proximal base of the apical 

 tooth. 

 Plants large ; well-developed leaves 



0.6 mm. or more in length. 

 Plants medium-sized ; well-dfevel- 

 oped leaves mostly 0.3-0.5 mm. 

 In length. 

 Plants small ; well-developed leaves 

 0.3 or less in length. 

 Lobule with a hyaline papilla at the 

 distal base of the apical tooth. 

 Perianth compressed, at least when young- 

 Lobule with a hyaline papilla at the 

 proximal base of the apical tooth. 

 Lobule with a hyaline papilla at the 

 distal base of the apical tooth. 

 Divisions of underleaves subulate and spread- 

 ing, 

 tf Plants more or less pigmented with brown. 

 ** Underleaves undivided. 



Plants pale green to yellowish green. 

 Sublioral innovations none. 

 Subfloral innovations present. 

 Plants more or less pigmented with brown. 

 Subfloral innovations none. 

 Subfloral innovations present. 

 Leaves densely squarrose. 



Perianth with five to ten keels. 

 Perianth with three keels. 

 Leaves not squarrose ; perianth with five 

 keels. 



b. Lobule usually inflated and helmet-shaped, usually 



attached to the lobe by a very short keel. 



1. Plagiochila. 



2. Radula. 



4. Leptocolea. 



3. Diplasiolejeunea. 



10. Taxilejcum u. 



5. Lejeunea. 



6. Microlcjeunca. 

 9. Euosmolejeunea. 



7. Reetolejcunca. 



8. Cheilolcjcunea. 



12. Leptolejeunea. 



11. CcratoUjcunea. 



1.'. Cuiiiliih jcunfu. 

 18. Leucolejeunea. 



14. Lopholejeunea. 



1.'!. lirachiolcjcunea. 



16. Musiii/iih ji ion a. 



17. .1 rchilejeunea. 

 10. Frullania. 



1. PLAGIOCHILA Dumort. Recueil d 'Obs. 14. 1835. 



Stems ascending from a prostrate rhizome, simple or with lateral branches. 

 Leaves succnbous, undivided, decurrent dorsally and ventrally, the margin 

 varying from entire to ciliate or spinose. Under-lraves usually minute and short- 

 lived. Inflorescence dioecious. Antheridia from one to ten in the axils of 



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