20 HEPATIC^. 



species both foliose and frondose hidden in twos and threes, in 

 small cavities of the epidermis arranged on both sides of the 

 stem ; or in others contained in open monandrous cavities supplied 

 with a minute incurved bract. Perianth incompletely tubular 

 (perfectly so in Pallavicinia only) ; in many species, however, 

 none is present. Calyptra not often small, generally long and 

 fleshy, free from the involucre and perianth, but often more or 

 less deeply concrete with the receptacle. Sterile pistillidia either 

 more or less deeply adnate to the calyptra (sometimes only at the 

 apex), or always arranged along the stem, naked. Capsule in 

 typical plants subglobose, formed of 2-5 series of cells, dehiscing 

 more or less irregularly. 



B. Elaters monospiral, very acute at each end ; but a few 

 short apical ones persisting longer. 



Subtribe yill. METZGERIEiE. 



Plants frondose, dichotomous or pinnately branched, the 

 lacinise linear; branches in the genus Aneura all lateral, the 

 nerve broad laxly cellulose, radiculose beneath, lamina none or 

 very narrow, rarely of moderate breadth; in the other genus> 

 Metzgeria, branches extremely seldom lateral and pinnate, all 

 the floriferous ones (sometimes even those that do not bear 

 flowers) postical, radicles springing from the nerve and the 

 margin, now and then from the whole surface. Reproductive 

 organs of both sexes distichous on the nerve of a shortened 

 branch; pistillidia 2-20 pairs, styleless ; antheridia very fre- 

 quently more numerous, very rarely tetrastichous. Perianth 

 none. Calyptra large, obovate, fleshy, in Aneura very often 

 papillose, in Metzgeria hairy with radicles. Capsule elongate, 

 quadrivalvate to the base, of two series of cells. Apical elaters 

 fixed and interwoven with others that are free, stretched out in 

 four pencils above the open capsules. 



