DIMORPHISM OF FERNS. 



275 



divisions of the pinnae, are inrolled into little spherical masses 

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

 these pinnules we find that there are several fruit dots within 

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



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 with 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 



