METAMORPHOSIS. 213 



have been made as to the conclusions to be drawn 

 from each phenomenon described under the heading 

 of Metamorphosis. Partial phyllody of the fertile 

 frond-segments of Ophioglossacege and of the fertile 

 fronds of the other ferns may be regarded as reversions 

 to that condition, obtaining in most modern ferns and 

 in the ancient Marattiacese, in which fertile and sterile 

 regions of the sporophyll were not so strictly and 

 widely segregated as they are in these forms in which 

 the abnormality occurs. Complete phyllody of the 

 fertile portions, as described in Botrychium and Aneimia, 

 is merely the extreme swing of the pendulum in the 

 same direction, and has, of course, no reversionary 

 meaning, for the leafy sporophyll, and not the oiit and 

 out foliage-leaf, was of necessity the original ancestor. 

 The abnormality in Equisetum may possibly stand 

 for a reversion to the character obtaining in the 

 immediate ancestry, viz. in such forms as Phyllotheca, 

 in which whorls of vegetative leaves alternated with 

 those of sporophylls, a condition found also in the 

 CalamarieEe. 



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