DEFINITIONS OF TERMS. 



a pinna all the parts thus separated being designated, 



in the aggregate, pinna. The pinnse may be entire, 



simply or deeply indented, or again, 



and more elaborately, divided. If 



twice so divided, taking the entire 



form as the starting-point, the frond 



is bi-pinnate, and if once more, or 



thrice divided, it is tri-pinnate. It 



is decompound if more than three 



times divided. The parts into which 



pinnae are immediately subdivided 



are termed pinnules. The immediate 



subdivisions of pinnules are lobes. 



Thus a thrice-divided frond, such 



as that of the Bracken, consists of 



stipes, rachis, secondary rachides, 



pinnae, pinnules, and lobes. 



The seeds of ferns, differing es- 

 sentially from the seeds of flowering 

 plants, are called spores. They are 

 dust-like bodies infmitesimally small, 

 and are enclosed on the backs or 

 along the under edges of the fronds 

 in a particular order in differently- 

 shaped spore-cases called sporangia. 

 The sporangia are generally pro- 

 duced in clusters or heaps called 

 son', each individual cluster being 

 called a sorus. 



In the figure of a pinna of the 

 Broad Buckler Fern on page 5, 

 the arrangement of these heaps or 

 clusters of spore-cases was indicated. 

 Here (page 14) is a magnified lobe of 

 a pinnule of the same frond, magni- 

 fied so as to show very clearly its iorm, and the form 

 and position of each sorus with respect to the veins of 

 c 2 



