Ferns : Habitats, Life-Story, Morphology 



patches or lines ? They are clusters of fruit-cases or 

 capsules. Each cluster, called a " sorus " (plural, " sori "), 

 has, in its early stages at least, a covering termed an 

 "indusium," which is an outgrowth from the under- 



FIG. i. FERN FROND. (AFTER LUERSSEN.) 



From " An Introduction to Structural Botany" by D. H. Scott. 



A, Leaf of male fern (much reduced) ; B, part of a fertile pinna seen from 

 below ; a, rachis ; j, sorus (magnified). 



surface of the frond. It may be well to note in pass- 

 ing that in some ferns this indusium is never present. 

 The shape or form of the indusium, linear, circular, 

 or kidney-shaped, is of great assistance to us when we 

 are identifying ferns that is, finding out their names. 

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