Annals 



of the 



Missouri Botanical Garden 



Vol. 9 SEPTEMBER, 1922 No. 3 



A MONOGRAPHIC STUDY OF THELYPODIUM AND ITS 



IMMEDIATE ALLIES 1 



EDWIN BLAKE PAYSON 



Formerly Teaching Fellow in the Henry Shaw School of Botany of Washington 



University 



Associate Professor of Botany, University of Wyoming 



Introduction 



The present study was made with at least two objects in 

 view ; it was desired to continue investigations on the phylogeny 

 of the Cruciferac and at the same time to attack a problem that 

 would yield results of practical taxonomic value. These two ob- 

 jects, although distinct in their purpose, were of course very 



•oughout the work. The taxonomy is but 

 ■nhvloffonetic conclusions. Recent studies 



associated th 

 ression of th< 



in this family have emphasized the necessity of detailed exam- 

 ination of the various generic units before any general develop- 

 mental theory is possible. The present author holds that there 

 is no basis for a study of phylogeny equal to a taxonomic re- 

 view of the species and genera involved. Details of specific dis- 

 tinction are most important in illustrating the steps in progres- 

 sive differentiation. The present view held is that phylogenetic 

 theories that do not take into account the apparently trivial de- 



f specific characterizations are not dependable 



subject 



f 



of 



taxonomist's part is to lay down the broader lines of 

 : and generic change and point the direction of the 

 troprrpss Where he leaves off. the work of the geneti- 



'An investigation carried on at the Missouri Botanical Garden in the Graduate 

 Laboratory of the Henry Shaw School of Botany of Washington University, and 

 submitted aa a thesis in partial fulfillment of the requirements for the degree of 

 doctor of philosophy in the Henry Shaw School of Botany of Washington Uni- 



versily. 



Issued February 16, 1923. 



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