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A revision of the genus Mitella with a discussion of 



geographical distribution and relationships. 



By 



C. otto Rosendahl 



With 9 fig. and 1 chart. (Table VIII.) 



Part, I, Introductory. 



The genus Mitella has experienced at the hands of systematic workers 

 a degree of splitting up into petty genera which is wholly inconsistent 

 with its well-marked generic characters and which does violence to the 

 lines of genetic development running through the group. The divisions 

 in all cases have been made upon one or two characters which are obvious 

 and artificial rather than fundamental, and the resulting genera, although 

 easy enough to recognize, are wholly artifical and arbitrary. 



It has always been one of the common weaknesses of taxonomic work 

 to employ single characters and greatly to overestimate their importance 

 •n distinguishing groups or constructing schemes of classification. The evil 

 results of such procedure are well illustrated in the breaking up of the 

 genus under discussion. Another pernicious practice is that pursued in 

 many floras of proceeding to slash and dismember families and genera on 

 the basis of only the material represented within the geographical limits of 

 the particular flora, when the probabilities are that many, yes often a 

 Jarge proportion, of the genera and species occur only outside such area. 



'o 



history 



genus Mitella and see what vicissitudes it has gone through, but lack of 

 space prevents such details. Since the latest monographic work on the 

 genus by P. A. Rydberg in the North American Flora, Volume 22, Part 2, 

 pages 91—96, 1905, — embodies all the important divisions that have 

 at different times been suggested, it will be sufficient for our purpose to 

 refer in detail only to this latest work. 



In his treatment of the group. Mr. Rydberg carries the splitting-up 

 tendency to the greatest extreme. Every section of the old genus, except 

 one, is raised to generic rank, varieties are made into species and many 

 new species are described. Where Engler in 1890 recognized one genus 

 and seven species, including one from Japan, this latest work recognizes 



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