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SUMMARY. 



Introduction. 



This work is not a mere descriptive tabulation of 

 interesting and curious " freaks," but is intended as a 

 contribution to the evolutionary origin of plant-organs. 



Of these there are three categories only : root, stem, 

 and leaf, although, in reality, the stem is non-existent, 

 being composed of leaf-bases. 



Of the four methods of morphological investigation, 

 viz., the developmental, anatomical, comparative, and 

 teratological, the last two are the only reliable ones. 



All abnormalities are not reversions, for many are 

 progressive in nature. 



As regards the value of abnormalities for the 

 elucidation of morphological problems, the opinion 

 of botanists is divided. The present writer attaches 

 great importance to teratological data for the inter- 

 pretation of structures of doubtful nature, and cites 

 leading authorities in support of this conclusion. 



An attempt is made, wherever possible, to answer 

 the question " why " an abnormal structure is present, 

 as well as " how " it came about. All structures, 

 whether normal or abnormal, are regarded as pur- 

 posive rather than fortuitous in their origin. They 

 are originated and maintained by the action of a 

 regulative vital force, and not by mere chemico- 

 physical energies. Hence, throughout the work, the 

 dynamic teleological or vitalistic position is upheld as 

 against the mechanistic or materialistic one. 



Fungi. 



The subaerial portion of the plant in the higher 

 forms tends to exhibit many of the same types of 

 abnormalities as are met with in the vascular plants. 



