I. INTRODUCTION 



The genus Marchantia is almost world-wide in its distribution 

 and includes some of the largest and most conspicuous of the 

 Hepaticae. According to the current rules of nomenclature the 

 genus was not definitely established until 1753, when Linnaeus 

 published it in the first edition of his Species Plantarum, but 

 the use of the name Marchantia dates from the year 1713. 

 Linnaeus recognized seven species, only the first two of which, 

 M. polymorpha and M. chenopoda, are now retained in the genus. 

 The type species, M. polymorpha, he cites from Europe only, 

 and gives Martinique as the habitat of M. chenopoda. At the 

 present time M. polymorpha is known to be almost cosmopolitan, 

 while the range of M. chenopoda, although apparently restricted 

 to tropical America, is likewise very extended. 



For a long time M. polymorpha was the only species recognized 

 in Europe. In 181 7, however, a second species, M. paleacea, was 

 described by Bertolini^ from material collected in Italy. This 

 species had been distinguished and figured by Micheli^ nearly a 

 century earlier but had not been accepted by Linnaeus. It is 

 now known to have a wide distribution in tropical and subtropical 

 regions, its range extending far beyond the confines of Europe. 

 Other European species which have been proposed from time 

 to time, such as M. macrocephala Corda and M. Sykorae Corda, 

 have never received wide acceptance and imdoubtedly represent 

 mere forms of M. polymorpha. 



The history of the genus in America, when the entire continent 

 is considered, is very much involved. This is due partly to the 

 full representation of the genus and partly to the confusion 

 which has arisen in the interpretation of certain species. 

 Before the publication of Gottsche, Lindenberg and Nees von 

 Esenbeck's Synopsis Hepaticarum, in 1847, the following species 

 of Marchantia had been recorded from North and South Amer- 

 ica: M, papillata Raddi (1823) from Brazil, M. platycnemos 

 Schwaegr. (1827) from Brazil, M. Szvartzii Lehm. & Lindenb. 

 (1832) from Jamaica, M. squamosa Raddi (1832) from Brazil, 



^ Opus. Sci. Bologna i : 242. 1817. 



' Nova Plant. Gen. 2. pi. i, f. 4. Florence, 1729. 



