n MUSCINE^—HEPA TIC JE— MARCH AN TI ALES 41 



guay. This interesting form has also been carefully examined 

 by Leitgeb ((7), iv., p. 34), who calls attention to its inter- 

 mediate position between the RicciacCce and the Marchantiacese. 

 The thallus has all the characters of the latter : air-chambers 

 opening by regular pores, usually surrounded by six guard- 

 cells; two rows of ventral scales, independent from the begin- 

 ning; and the sexual organs united into groups upon special 

 parts of the thallus. The sporogonium, however, is entirely 

 like that of Riccia, so that it may properly be placed in the same 

 family. The plants are dioecious and strictly terrestrial. 



A third genus, Cronisia, represented also by a single species, 

 C. paradoxa, is placed provisionally with the RicciacCcC by 

 Schiffner ((i), p. 15), but the structure and development have 

 not been investigated with sufficient completeness to make this 

 certain. It has been found only in Brazil. Schiffner says of 

 this form : 'Tt belongs perhaps to the Corsinie?e, and forms 

 a direct transition from the Ricciaceae to that family." 



The C0RSINIACE.E {Schiffner (i), p. 26), 



The family Corsiniacese comprises but two genera, Corsinia 

 and Ftmiciilaria (Boschia). Each genus contains but a single 

 known species. Structurally they are intermediate in character 

 between the Ricciace?e and Marchantiacese. Corsinia differs 

 from all the higher Marchantiacese in the character of the ven- 

 tral scales, which are formed in more than two rows, like those 

 of Ricciocarpns. Boschia, the other genus, has two rows of 

 scales of the ordinary form. The archegonia are borne in a 

 group in a depression upon the dorsal surface of the thallus, but 

 are not formed upon a special receptacle, although after fertili- 

 sation the cells at the bottom of the cavity multiply actively and 

 form a small prominence upon which the young sporogonia are 

 raised, and this may perhaps be the first indication of the arche- 

 gonial receptacle in the other forms. 



The sporophyte resembles that of the Marchantiacese, but 

 the sterile cells in Corsinia do not develop into true elaters, and 

 in both genera the foot is less developed than in the true Mar- 



chantiaceae. 



March ANTiACE^. 



Comparing the Marchantiaceae with the Ricciaceae, the close 

 similarity in the structure and development of the thallus is at 



