162 



STRUCTURE AND LIFE HISTORIES 



and sporophylls are very closely related to each other, 

 and demonstrate clearly that foliage-leaves may be 



FIG. 122. Walking fern (Camptosorus rhizophyllns). The smaller, 

 lower plant originated at the tip of a leaf of the larger plant, and one of its 

 leaves has, in turn, struck root. 



produced by the sterilization of spore-bearing leaves. 

 The interesting question here naturally arises as to 



