Ill] THE BRACKEN FERN 37 



that in many or even in most of them the margins 

 are curved downwards, and extended into a pellucid 

 veil or indusium, so that what appears from above to 



Fig. 6. Vertical section through a fertile leaf, of Nephrodhim 

 traversing a single sorus. This is attached to one of the veins 

 of the leaf which is enlarged as the receptacle. Upon it are 

 seated the numerous stalked sporangia, each containing many 

 dark-walled spores. The whole is covered over by the umbrella- 

 like indusium. (After Kny.) 



be the margin is really a curved and slightly swollen 

 region extending into a continuous protective fla[). 



