PREISSIA. 473 



unequally 4 or 5 parted. Calyptra persistent, rupturing obliquely 

 at the apex. Capsule large, shortly pedicellate, dehiscing by 

 4 or 8 irregular revolute valves. Spores large, tuberculate. 

 Elaters short, bispiral. Male receptacle pedunculate, peltate, 

 repand, lobate. 



Preissia commutata [Lindenb.), Nees. 



Marchantia hemispharica , Linn. Fl. Suec. ii. 1052 (1745). 



Marchantia quadrata, Scop. Fl. Carn. t. 63, 1356 (1772). 



Marchantia commutata, Lindenb. Hep. Eur. p. 101 (1829). 



Marchantia androgyna, Tayl. in Trans. Linn. Soc. xvii. p. 380 (1835). 



Preissia commutata, Nees, Nat. Eur. Leber, iv. p. 117 (1838). 



Preissia hemisp/uerica, Cogn. in Bull. Soc. Bot. Belg. p. 49 (1872) ; Dum. Hep. 



Eur. p. 152 (1874). 

 Chomiocarpon quadratus (Scop.), Lindb. Muse. Scand. (1879). 



Dioicous, closely ca?spitose, medium size, pale green to 

 brownish-green antically, dark purple postically and at the 

 margin. Fronds prostrate, oblong-sinuate, apices bilobed, 

 porose, margin irregularly crenate, on the postical side 

 squamose, scales purplish-black, oblong, acinaciforni. Female 

 flowers pedunculate, peltate, angularly hemispherical or sub- 

 quadrate, sub-entire or lacerate, above obtusely 4-costate, 2-4-lobed, 

 loculi attached to the underside of the lobes, 1-3-fruited, de- 

 hiscing irregularly. Perianth obconico-campanulate, 4-5-lobed. 

 Peduncle below red, above pale green, bicanaliculate, channels 

 on both sides with rootlet-threads. Calyptra rotundate, 

 styled, persistent. Capsule globose, shortly pedicellate, reddish- 

 brown or dark purple, dehiscing by revolute segments, cells 

 of the inner wall with reddish-brown ring fibres. Spores 

 brown, submuricate, roundish-tetrahedral. Elaters long, slender, 

 bispiral. Male receptacle pedunculate ; peduncle very thick, 

 obtusely angular and irregular in outline, outer walls dark 

 purple, 1 or 2 inner layers purple, others hyaline, trigones 

 large, walls thin, bicanaliculate, with rootlet threads in the 

 channels; smaller than the female, often subsessile; peltate, 

 margin scariose, thin, undulate, irregular but undivided ; 



