FERNS 189 



highest, is felt to be the one between Bryophytes and 

 Pteridophytes. On account of the vascular system and 

 other resistant structures, the remains of ferns have been 



FIG. 181. Cross-section of the stem (rootstock) of a fern, showing the peculiar 

 vascular axis, the large xylem vessels being completely surrounded by the 

 phloem. 



preserved in great abundance in the rocks. These records 

 show that the ferns are a very ancient group, occurring 

 in special abundance during the Coal-measures. 



Another striking fact about this leafy body of the 

 ferns is that it never produces sex-organs, but does produce 

 spores abundantly. This means that it is the sporophyte 

 in the life-history of the fern, and when it is contrasted 

 with the sporophyte of Bryophytes the differences are 

 remarkable. Among the liverworts and the mosses the 

 sporophyte is a leafless structure attached to the gameto- 

 phyte and dependent on it, while the gametophyte is the 

 leafy body doing chlorophyll work. Among the ferns, 

 however, the sporophyte is an elaborate leafy structure 

 and entirely independent. Therefore, when one ordinarily 



