Helianthus 



Compositae 



975 



o 5o 



Map 2129 



Helianthus rigidus (Cass) Desf. 



o ^13 

 Map 2130 



Helianthus microcephalus T. & G 



50 

 Map 2131 



Helianthus divancatus L 



sions in black oak woods, at the bases of the slopes of black cak woods, 

 and sometimes on sandy knolls and ridges. In addition to the area shown 

 on the map it has been reported from Vigo County where it doubtless 

 formerly occurred. 



Ohio to Minn., southw. to Ga. and Ark. ; introduced into N. E. and N. J. 



5. Helianthus rigidus (Cass.) Desf. (Helianthus scaberrimus of In- 

 diana authors.) Prairie Sunflower. Map 2129. This is a typical prairie 

 species and is frequent in the "western prairie" area of the state. It is also 

 local in other parts of the state in relict prairie areas. 



According to Watson it is common in plains and moist prairies from 

 western Canada to Texas; introduced and becoming common east of the 

 Mississippi River but rare in the eastern United States. 



5a. Helianthus rigidus (Cass.) Desf. forma flavus, f. nov., disco flavo. 

 (Helianthus laetiflorus Pers. of Indiana authors.) Disk flowers yellow. 

 The type, Deam, no. 57312, was found in a prairie habitat in Newton 

 County, Indiana, and is deposited in the Deam Herbarium. So far as I can 

 determine the species and form are exactly alike except in the color of the 

 disk flowers. I suspected this and in 1936 I cruised the western part of 

 the state for over a thousand miles to learn if both the red and yellow 

 forms could be found in the same colony. At last I found a small red 

 colony with a single yellow flower in it. 



I am interpreting this form as an "albino" of the species. I believe the 

 yellow flowered form is simply a strain of the species that is no longer 

 able to develop the anthocyanin of the species. For an exhaustive treat- 

 ment of the subject see Onslow's "The Anthocyanin Pigment of Plants." 



Probably throughout the range of the species. 



6. Helianthus microcephalus T. & G. Small Wood Sunflower. Map 

 2130. This is strictly a woodland sunflower and is well but sparsely dis- 

 tributed in the southern part of the state. It does not form colonies like 

 most of our sunflowers and usually only a single specimen or a few are 



