578„ MOSSES AND FERNS chap. 



Marchantia — perhaps identical with it. From the amber of 

 North Germany, also of the Oligocene, a number of Liverworts 

 have been described, all being referred to living genera, e. g., 

 Frullania, Jungermannia. 



The higher Mosses might be expected to leave more evident 

 traces than the more delicate Liverworts; but although many 

 moss-like fragments have been described, the real nature of 

 most of them is doubtful, as they are for the most part merely 

 impressions and might very well belong to other plants than 

 Mosses. While it is extremely probable that some of the 

 species of ''Musettes" are real Mosses, and that Mosses were 

 present in the Palaeozoic formations, it cannot be said that our 

 knowledge of these forms is very satisfactory. 



Some of the larger Mosses, like Polytriehum and Hypnum, 

 might very well be preserved fossil ; but unfortunately their 

 resemblance to the shoots of small Lycopods, or even of some 

 Conifers, is so close that their identification from impressions 

 is practically impossible. Except in the later formations no 

 trace of the characteristic sporogonium has been found, and 

 even in the few instances from the later formations, the real na- 

 ture of the fossils is not beyond question. While it is reason- 

 able to suppose that both Liverworts and Mosses occurred in 

 the Palseozoic formations, there is no certain evidence of this 

 from the geological record, and such fragments as do occur in 

 the Palaeozoic rocks are too uncertain to throw any light upon 

 the origin of the Muscinese. 



Fossil Pteridophytes 



The firm tissues of the sporophyte in the Pteridophytes are 

 much more resistant than the soft tissues of most Bryophytes, 

 and consequently far better fitted to be preserved in a fossil con- 

 dition. Remains of undoubted Pteridophytes occur from the 

 Silurian, and in the Devonian and the succeeding Palaeozoic 

 formations they constitute the predominant plant types. It is 

 evident from a study of the fossil remains that all the existing 

 classes were well differentiated as far back as the record ex- 

 tends ; but in addition to these, there were a number of types 

 which have become extinct, the exact affinities of some of which 

 are not entirely clear. 



