DIMORPHISM OF FERNS. 



275 



divisions of the pinnse, are inroUed into little spherical masses 

 which lie close on the side of the pinna;. If we unroll one of 

 these pinnules we find that there arc several fruit dots within 

 protected by this roll. In fact when the spores are mature these 



■V, 4 ' -^u^' 



Fig. 317- 

 Sensitive fern ; one fertile leaf nearly changed to vegetative leaf. 



pinnules open somewhat, so that the spores may be dissemi- 

 nated. 



There is very little green color in these fertile leaves, and 

 what green surface there is is very small compared ^\'ith that of 

 the broad expanse of the sterile leaves. So here there is practi- 

 cally a complete division of labor between these two kinds of 



