332 BOTANICAL GAZETTE [November 



promoting a better evaluation of the North American species. 

 On two occasions I was permitted by Dr. Julius Nieuwlaxd to 

 study freely the specimens, several of them types, in the Greene 

 Herbarium at the University of Notre Dame. To all of these 

 botanists I here express my great indebtedness and gratitude. ' 

 Others to whom also I am grateful for assistance rendered are: 

 Dr. N. L. Brttton, Director of the New York Botanical Garden; 

 Dr. J. M. Greenman, Curator of the Herbarium, Missouri Botani- 

 cal Garden; Dr. Aven Nelson, President, University of Wyoming; 

 Professor \Y. W. Rowlee, Cornell University; Professor D. B. 

 Swingle, Botanist and Bacteriologist, Montana Agricultural 

 Experiment Station. 



Abbreviations used for Herbaria: HI). Boiss., Herb. Boissier; 

 Hb. Can., Herb. Canadian Geological Survey; Hb. Chi., Herb. 

 University of Chicago; Hb. Field, Herb. Field Museum of Natural 

 History; Hb. N.Y., Herb. New York Botanical Garden; Hb. 

 U.S., United States National Hebarium. 



Clavis specierum 



Achaenia matura rubescentia 



Folia plerumque gracilia, profunde laciniato-pinnatifida; involucri foliola 



exteriora plerumque patentia vel etiam recurvata 5. T. laevigatum 



Folia crassiora, minus profunde pinnatifida vel etiam integra; involucri 



foliola exteriora plerumque adpressa 3- T. eriophorum 



Achaenia matura non (nisi interdum versus apicem in num. 1) rubescentia 

 Achaenia matura nigrescentia (vel interdum versus apicem rubescentia) 



1. T. lyratum 

 Achaenia matura aliusmodi 



Involucri foliola plerumque adpressa et corniculis instructa 



2. T. ceratophorum 



Involucri foliola ecorniculata vel raro corniculis minimis instructa, exteriora 



patentia vel reflexa 4- T. vulgare 



1. Taraxacum lyratum (Led.) DC, Prodr. 7:148. 1838; 

 Leon tod on lyratusLedebom, Icon. PI. Fl. Ross. ill. 5:27. pi. 497. 1834; 

 Fl. Altaica 4:152. 1833; T. phymatocar pum Yahl. Fl. Danica 

 13 (fasc. 39) :6. pi. 2298. 1840; Watson, U.S. Geol. Explor. 40th 

 Parallel 207. 1871; T. laevigatum Gray, Proc. Acad. Phil. 1863, 

 p. 70 (non Willd.); T. officinale var. scopulonun Gray, Synopt. 

 Fl. N. Amer. i 2 :44o. 1884; T. Taraxacum var. scopulorum Heller, 



