VOLUME LXX 







NUMBER s 



THE 



Botanical Gazette 



NOVEMBER 1920 



NORTH 



\XACUM 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 272 



Earl Edward Sherff 



(with plates xxxi-xxxiii) 



For many years our knowledge of the American species of 

 Taraxacum has been in a very imperfect and chaotic state. The 

 perusal of the more prominent manuals and floras issued in the 

 United States during the past few decades shows a surprising 

 confusion of forms and multiplicity of specific names. This con- 

 fusion is easily accounted for by the fact that most of the Taraxacum 

 forms tend strongly to intergrade, so much so that many botanists 

 in the past have despaired of their specific segregation. Thus 

 Torrey and Gray (Fl. N. Amer. 2:494. 1843), a ^ ter describing 

 Taraxacum dens-leonis ( = 7\ vulgar e), wrote as an introduction to 

 their four additional species: "The following species (the characters 

 of which we copy from chiefly de Candolle, who keeps them dis- 

 tinct), as well as nearly all the genuine Taraxaca. are not improbably 



1 Including the West Indies, but not Greenland. The large number of new 

 1 species recently proposed for Greenland by Dahlstedt have made it inadvisable to 



I include the Greenland plants until a more abundant supply of Greenland materia! 



I can be obtained for detailed study. So far, however, I have examined no plant* 



I from Greenland that were not clearly referable either to those species included in 



I this treatment or to Taraxacum nivalc Lange, a species close to T. lyratum but differ- 



ing in having the achenes glabrous or nearly so. From a study of Dahlstedt's 

 work (Archiv f. Botanik 4 8 :i~4i. 1905; ibid., 5 9 :i"44. J 9o6) and those of his deter- 

 minations accessible to me, it appears that his "new species ,, are mostly synonymous 

 with Taraxacum lyratum, T. nivalc, and T. ceratophorum. 



329 







