HEPATICAE 49 



b. Capsule 4-valved to the middle or a little beyond only. 



I. Elaters deciduous, 2 — 3-coiled. 



(3) 23. Madotheca 



II. Elaters persistent on the valves, 1 -coiled. 



1. Perianth obtuse, not ciliate. (Figs. 40 and 41.) 



(10) 24. Frullania 



2. Perianth 3 — 4-lobed, ciliate. (Fig. 41.) 



(15) 25. Lejeunea 



B. Anacrogynae. 



Plant thalloid (exc. Fossombronia). Archegonia dorsal or lateral ; 

 sporogonia consequently dorsal or lateral. 



a. Plant thalloid. 



I. Elaters persistent on the top of the valves. 



1. Thallus fleshy, lobed, without a rib. 



(2) 26. Aneura 



2. Thallus thin, furcate, with a definite midrib. (Fig. 41.) 



(1) 27. Metzgeria 



II. Elaters persistent at the base of the capsule, or deciduous. 



1. Involucre of capsule double, the inner one long and tubular. 



(1) 28. Pallavicinia 



2. Involucre simple. 



(2) 29. Symphyogyna 



b. Plant leafy. 



(4) 30. Fossombronia 



Order II. MARCHANTIALES. 



A. Epidermal pores (stomata) wanting or rudimentary. Sexual organs em- 



bedded in open cavities upon the dorsal surface. Sporogonium 

 sessile, when ripe without wall, remaining permanently within the 

 wall of the archegonium. Elaters none. 



(8) 31. Riccia 



B. Epidermal pores fully developed. Sexual organs not embedded. Sporo- 



gone with a wall. Elaters present. 



a. Sporogone single on the ventral side of the lobes of the thallus. 



(1) 32. Targionia 



b. Sporogones in groups on special, long stalked receptacles. 



I. Stomata stellate. 



(1) 33. Plagiochasma 



M. 7 



