924 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The thallus is divisible into three distinct layers, the air-chamber 

 layer to which the stomata belong, the close tissue (without inter- 

 stices), and the ventral cortical layer. In the second of these are 

 found in all Marchantiese the mucilaginous organs described by 

 Goebel, of the function of which but little is known, and the oleagi- 

 nous bodies of Pfeffer. The third is more or less sharply differentiated, 

 and consists of one or more layers of cells. The leaf-like lamellfe on 

 the ventral side of the thallus are not properly leaves, being homo- 

 logous not to the leaves of the Jungermanniete, but to the ventral 

 scales of the EicciesB. The rhizoids are always of two kinds, ordinary 

 and conical. 



There is nothing fresh of importance respecting the fructification. 

 The receptacles, while still sessile, are bordered by " lacinise," or 

 enveloping scales ; these are dorsal trichomes, both in those genera 

 where the receptacles are purely dorsal structures, and in those where 

 the apex of the shoot persists on the receptacle ; while in those where 

 the receptacle corresponds to a branch-system, the outer enveloping- 

 scales certainly, and probably the inner ones also, are modified 

 ventral scales. The envelope of the archegonia arises, as in the 

 EiccieaB, by an overgrowth of the sexual organs, in consequence of the 

 luxuriance of the adjacent parts of the thallus ; while, on the contrary, 

 the "perianth" of the single archcgonium is, in Marchantia and 

 Preissia, a product of the pedicel of the archegonium. The develop- 

 ment of the sexual organs follows exactly the type of Riccia. The 

 description of the development of the sporogonium corresponds to 

 that of earlier observers. The bursting of the capsule takes place 

 either by teeth, in consequence of the formation of several longitu- 

 dinal slits proceeding from the apex (in all the genera with fibrous 

 thickening of the walls), or by the separation of the apical third of 

 the capsular wall in the form of a lid (in the genera with unthickened 

 or angularly thickened cell-wall). The splitting of the capsule is not 

 similar to that in the Jungermanniefe. 



As regards classification, Leitgeb proposes to abolish the division 

 into Lunulariefe, Jecoraricfe, and Targionieae. He prefers to include 

 Plagiocliasma, BebouUa, Grimaldia, Duvalia, and Fimbriaria, into 

 one section under the name MarcJiantiece opercidatce, distinguished by 

 the upjDer part of the capsular wall being sometimes thrown off in one 

 piece, sometimes breaking up into irregular plates, the lower part 

 always remaining entire. The second division, or AstroporcB, in- 

 cluding the genera Sauteria, Peltolcpis, and Clevea, is distinguished 

 by the stellate form of the stomata, caused by the strong thickening 

 of the radial walls of their marginal cells. In the third and highest 

 division, or Composifce, the receptacle is formed from a branch-system ; 

 it includes the genera FegateUa, Lunularia, Dumortiera, Preissia, 

 and Marchantia. Finally, the genera Targionia and Cyathodium 

 make up the Targioniece, in which the fructification stands on the 

 margin of the thallus, and is not borne on a receptacle. The whole 

 family of Marchantiacese is, therefore, divided into three groups 

 as follows : — 



1. Bicciece (Riccia, Eicciocarpus, Oxymitra). 



