EXPLANATION OF TERMS 



dots. They take various shapes in the different 

 species. They may be round or linear or oblong 

 or kidney-shaped or curved. At times they are 

 naked, but more frequently they are covered by a 

 minute outgrowth of the frond or 

 by its reflexed margin. This cov- 

 ering is called the indusium. In 

 systematic botanies the indusia V^^^^^^^ ^ 

 play an important part in deter- 

 mining genera. But as often they 

 are so minute as to be almost in- 

 visible to the naked eye, and, as 

 frequently they wither away early 

 in the season, I place little dependence upon them 

 as a means of popular identification. 



A fertile frond is one which bears spores. 



A sterile frond is one without spores. 



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