DIMORPHISM OF FERtfS. 



279 



Below these are other leaves which are different in form and 

 sterile. These leaves are broad and hug closely around the roots 

 and bases of the other leaves. Here they serve to catch and 



Fig. 320. 



Ostrich fern, showing one normal sporophyll, one partly transformed, and one completely 

 transformed, 



retain moisture, and they also catch leaves and other vegetable 

 matter which falls from the trees. In this position the leaves 

 decay and then serve as food for the fern. 



