AS COMPARED WITH THAT OF THE PRESENT DAY. 



409 



fructification, which proves them to belong to different groups of the 

 order. It has been already remarked that the fruit is rarely present in 

 fossil ferns ; whence it may be presumed, that did the four ferns just 

 described occur fossil, the probability is great that whatever formation 

 they inhabited, or however widely separated they were in geographical 

 position, they still would all be included under one species. 



Fig. 6. 



Again, very many existing species of ferns have the fertile frond 

 quite distinct from the barren ones in size and shape. The Niphobolus 

 rupestris of New Zealand is an instance : a wood-cut of it (Fig. 6) is 

 added. In such a case the absence of any fructification on the one 

 hand, and the severance of both the fertile and barren fronds from the 



