Rydberg : Rocky Mountain flora 329 



these two numbers of the Boundary Survey are in both the her- 

 barium of the Columbia University and that of the New York 

 Botanical Garden. The structure of the marginal achenes distin- 

 guishes B. Bigelovii at once from B. bipinnata. 



Thelesperma 

 In the description of Thelesperma ambiguiim in Coulter & Nel- 

 son's New Manual, we find the following: "bracts of the outer 

 involucre 8, subulate-linear, almost equalling or half the length 

 of the inner," etc. In Wright's specimens, from which T. am- 

 biguiim was described, the outer bracts are ovate or elliptic, 

 scarcely one fourth as long as the inner involucre. What is de- 

 scribed in the New Manual is evidently T. intermedium Rydb. 

 When I described the latter, I had known it for about ten years 

 and had never been able to make it agree with Dr. Gray's descrip- 

 tion of T. ambiguiim in the Synoptical Flora. In the original 

 publication of Thelesperma ambiguiim no diagnosis is given, only 

 a few characters distinguishing it from related species. In habit 

 T. ambiguiim resembles most T. subnudum, having the creeping 

 rootstock of that species, the long naked peduncles, and the leaves 

 found near the base of the stem only. The range is given as 

 Montana to New Mexico and Texas. This was probably taken 

 from the Synoptical Flora. The specimens on which Dr. Gray 

 extended the range to Montana belong to T. marginatum, in 

 many respects closely related to T. ambiguiim but with discoid 

 heads. T. ambiguiim, as far as I know, is not found north of 

 southern Colorado. T. intermedium, which is really described 

 under the name of T. ambiguum in the New Manual, does not 

 have a "creeping rootstock" (as Gray described T. ambiguum) 

 but has a biennial or perennial taproot; and it has a leafy stem. 

 As the authors of the New Manual did not at all consider the dif- 

 ferences in the subterranean parts of T. ambiguum and T. inter- 

 medium, it was natural that they would not consider the same 

 parts in T. trifidum and T. tenue, which resemble each other much 

 more closely, and we find the latter as a synonym of the former. 

 Thelesperma marginatum Rydb. is ignored altogether, although in 

 my Flora of Montana four collections from that state are cited. 



