XVI FOSSIL ARCHEGONIATES 577 



the reader is referred to Professor Seward's "Fossil Plants" 

 (Seward (i), Chap. IV). By grinding thin slices of these 

 petrified tissues, they may be examined microscopically with as 

 much ease as sections taken from living plants, and it is largely 

 to a critical study of such petrified tissues that the affinities of 

 many doubtful forms have been determined. 



In some of the later formations delicate plants, like Mosses 

 and Liverworts, have been preserved in amber, and of course 

 in these cases, there is no question of the nature of the plants ; 

 but no such fossils occur in the older formations, and none of 

 those discovered are essentially different from their existing 

 relatives, and of course throw no light upon the early history 

 of the Archegoniates. 



The fossil remains of the lower plants are for the most part 

 extremely meagre, and throw little light upon the evolution of 

 the Archegoniates. Presumably the progenitors of the lower 

 Archegoniates were simple Green Algse, but such extremely 

 perishable organisms can hardly be expected to have left recog- 

 nisable remains in the older rocks. Some of the calcareous 

 Algae like the Characese, certain Siphonese and Corallines, are 

 known from very old strata, and there is every reason to be- 

 lieve that the less specialised Confervoidese, which probably are 

 nearer the lower Archegoniates, were also abundantly repre- 

 sented in the earlier geological epochs, although they have left 

 no recognisable fossil traces. The delicate nature of the prim- 

 itive Hepaticas fully explains their absence from the earlier 

 strata, and the same is true of the gametophyte of the Pterido- 

 phytes. 



Fossil MusciNE^ {Seward (i), Chap. VIII) 



The fossil remains of Bryophytes are too scanty in number 

 and of too doubtful authenticity in most cases to be of much 

 value in determining the geological history of the group. 

 Liverworts are too delicate to leave fossil traces except under 

 most exceptional conditions. In the Tertiary and later forma- 

 tions they are occasionally met with, but all the forms discov- 

 ered are closely allied to existing species, and throw no light 

 upon the origin of the Hepaticae. Of the few unmistakable 

 fossil Hepaticse, may be mentioned Marchantites Sesannensis, 

 of Oligocene Age. This is evidently close to the living genus 

 37 



