970 



COMPOSITAE 



Helianthus 



^0 



Map 2123 



Ratibida pmnata (Vent.) Barnh. 



Miles 

 50 



Map 2124 

 colummfera (Nutt 



Woot & Standi 



of this species collected in 1929 by Robert Hessler along the B. &. 0. Rail- 

 road about a mile and a half east of Irvington in Marion County. The 

 rays are entirely yellow. Hessler found only two specimens. Peattie reports 

 it as naturalized in the Calumet District of Lake County but he does not 

 tell us how abundant it is there. This species may be only a railroad 



migrant. 



Dry prairies, Minn, to Sask. and B. C, southw. to Term., Tex., and Ariz. 



9200. HELIANTHUS L. Sunflower 



[Watson. Contributions to a monograph of the genus Helianthus. Papers 

 Michigan Acad. Sci. 9: 305-475. 1929. Johns. Heliantheae of Iowa, III. 

 University of Iowa studies in natural history, New Ser. 295: 337-416. 

 1935.] 



I have given this genus considerable study not only in the herbarium and 

 in the field but I have had most of our species under cultivation for several 

 years for observation. Prof. Elba E. Watson named all of my specimens up 

 to 1936 and I had for study the large collection of Ralph M. Kriebel which 

 was named by Watson. I at first attempted to construct a key to our species 

 using Watson's determinations. This I was not able to do. Prof. Watson 

 in his monograph says : "Related species have a most perplexing tendency 

 to fade into one another and in such a way that, while the typical extremes 

 are readily enough recognized, there will always be a large number of 

 plants that will not fully satisfy the definition of either of two species, and 

 that can be as logically placed with one as with the other. This is fla- 

 grantly true of three groups" which ne discusses in detail. I agree with 

 the preceding statement. 



The sunflowers are extremely responsive to soil, light, moisture, and 

 crowded conditions. Some authors credit hybridization for many depar- 

 tures from the normal species. I have not seen a specimen which I believe 

 to be a hybrid. I have had 12 species under cultivation for a number of 

 years and to prevent them from spreading I restricted them to their beds 

 about three feet in diameter by bands of galvanized iron placed below the 



