Rydberg : Studies on the Rocky Mountain Flora 632 



T. iiitcnncdiinn grows in sandy or loose soil, often taking pos- 

 session of old fields and acts much like a weed. The following 

 specimens are at hand. 



Nebraska : Banner County, 1 890, Rydberg, ig2 (type) ; 

 Crawford, 1889, H.J. Webber. 



Wyoming: Pine Bluffs, 1897, Aven Nelson, Jjoj. 



Colorado : 1862, //a// & Harbour, 2S0, at least in part. 



Colorado or Wyoming : 1843, Fremont. 



New Mexico : Between Santa Fe and Canoncito, 1897, A. A. 

 & E. Gertrude Heller, 3747. 



4. Tiielesperma ambiguum a. Gray, Proc. Am, Acad. 19: 16. 



1883 

 This species seems to be confined to the plains of western 

 Texas, New Mexico and southern Colorado. The specimens re- 

 ported from Nebraska and Wyoming belong mostly to the preced- 

 ing, and those from Montana to T. marginatum. The latter 

 resembles T. ambiguum in many respects, especially as to the in- 

 volucral bracts ; but it is always without ray-flowers. 



5. Thelesperma subnudum a. Gray, Proc. Am. Acad. 10 : 72, 



1874 



This is an inhabitant of the more arid regions of New Mexico, 

 Arizona, Utah and Colorado. 



6. Thelesperma marginatum Rydb. Mem. N. Y. Bot. Garden, i : 



421. 1900 



This grows on dry plains of Alberta and Montana. 



7. Thelesperma gracile (Torr.) A. Gray, Kew Journ. Bot. i : 



253. 1849 



Bidens gracilis Torr. Ann. Lye. N. Y. 2 : 215. 1827. 



This species is the most common and most widely distributed 

 species of the genus. It is common on dry plains from Nebraska 

 to Montana, Arizona, Mexico and Texas. 



HYMENOPAPPUS L'Her. 



Throat of the corolla 1-I.5 mm. long, not over twice as long as the lobes. 

 Pappus over l mm. long, equaling the corolla-tube or nearly so. 

 Stem 3-6 dm. high, leafy throughout ; heads numerous. 



