









i9*>] SIIERFF—TA RA XA CUM 



331 



the conclusions for their easier accessibility to American students. 



Mazzetti 



I nor has it been attempted to repeat his extensive lists of synonyms 



J in full. Only such synonyms are given as seem vital or as were 



misplaced or overlooked by him. For the sake of comparisons, 

 however, his excellent specific descriptions have been followed 

 closely; in the main, only such alterations have been made as 

 considerations of brevity or accuracy would dictate. 



Since the completion of my research there has appeared the 

 recent article by Stork (Bull. Torr. Bot. Club 47: 199-210. pis. 6 y 

 7. 1920). It contains interesting data concerning sexuality, varia- 

 tion, and cytological aspects of certain American species, and cites 

 several references that must be omitted here. 



As may be noted in the following pages, I have found no occasion 

 for proposing a single new species. In fact the literature of the 

 genus has suffered seriously in the past from the persistent and 

 repeated proposal of ill-advised and scantily considered specific 

 names, many of them founded upon freakish or even immature 

 material. Rather have I been compelled to reduce three species 

 retained by Handel-Mazzetti (T. phymatocarpum, T. mexicanum, 

 and T. lapponicum) to synonomy, thus giving a total of only 



five 



species in our range. 



Most of the work was prosecuted in the Herbarium of Field 

 Museum, where I was afforded the fullest measure of freedom 

 and courtesy through the kindness of the Curator, Dr. Charles F. 

 Millspaugh. The entire collections of Taraxacum in the United 

 States National Herbarium, especially rich in specimens from 

 Alaska and the Arctic regions, were loaned through the generosity 

 of the Associate Curator, Mr. William R. Maxon. All of the 

 highly important materials in the Herbarium of the Canadian 

 Geological Survey were loaned by Professor James M. Macoun, 

 late of that Herbarium. Among these were a vast number of 

 valuable specimens from western Canada and the Arctic regions. 

 All of the nearly 800 specimens in the Herbarium of Boissier and 

 the Herbarium of the Institut de Botanique, Geneva, were loaned 

 by Dr. R. Chodat. These, while mostly from Europe, Asia, and 

 elsewhere than from North America, were of the greatest value in 



