THE EVOLUTION OF PLANTS 235 



ancestors of our modern conifers and angiosperms, must 

 be imagined as hidden in the recesses of the forest. 



151. Significance of the Fossil Record.- Before the 

 brilliant discoveries in fossil botany, just outlined, were 

 made, there had been (as stated in Chapter VI) a general 

 tendency among botanists to consider the comparatively 

 simple moss-plants as an older type than the fern, and 

 that either they or their close relatives were the ances- 

 tors of Pteridophytes. As outlined in the same chapter, 

 the sporogonium of the moss was regarded as representing 

 the form from which, by elaboration of vegetative tissues 

 and organs, the sporophyte of the fern was derived. This 

 view was clearly expressed in 1884 by the noted botanist 

 Nageli, who considered that the sporophyte of Pterido- 

 phytes was derived from a moss-like sporogonium by the 

 development of leafy branches. 



A consideration of the fossil record, however, makes it 

 difficult to accept this hypothesis. Not only do we find, 

 in the fossil forms described above, sporophytes that do 

 not bear the remotest resemblance to the moss-sporo- 

 gonium, but fossil mosses and liverworts have never been 

 positively identified in either the Palaeozoic or the Meso- 

 zoic rocks, 1 while the same rocks are rich in fossils of such 

 advanced forms as the broad-leaved sporophytes of the 

 Cycadofilicales and Cycadophytes. We must not, how- 

 ever, hastily conclude, from this lack of evidence, that 

 mosses and liverworts did not exist in those early ages. 

 Quite possibly they were present when the Paleozoic rocks 

 were being deposited, though doubtless not represented by 

 the same genera, or at least not by the same species, as 

 are now living. 



l Cf., however, p. 172. 



