II. SPECIES INFORMATION 

 A. CLASSIFICATION 



1. SCIENTIFIC NAME: Cirsium subniveum Rydb. 



2. COMMON NAME: Jackson's Hole thistle. 



3. FAMILY: Asteraceae (=Compositae, Sunflower 

 Family) . 



4. GENUS: According to Hitchcock et al. (1955), 

 there are perhaps as many as 200 species of 

 Cirsium native to the northern hemisphere, with 

 about 50 native species occurring in North 

 America. The genus Cirsium is most closely allied 

 with the strictly Old World genus Carduus . Dorn 

 (1984) lists 13 species of thistle for Montana, 

 several of which are introduced. 



5. SPECIES: Recently, there was some confusion in 

 Montana of Cirsium subniveum with C. neomexicanum 

 var. utahense. In 1988 a collection from French 

 Creek ( K. Scow and E. Darfler (s.n.) . 1988, MONTU) 

 was identified as C. neomexicanum var. utahense by 

 G. Ownbey. This author made a second collection 

 from the same site ( Schassberger (405) . 1990, NY), 

 which better fit the description of C. subniveum , 

 and was identified as such by Dr. Arthur Cronquist 

 (pers. coram. 1991) , New York Botanical Garden. 

 The Scow and Darfler collection was subsequently 

 sent to Brigham Young University, and annotated C. 

 subniveum by Dr. S. L. Welsh. The closeness of 

 these two easily confused taxa was noted by 

 Cronquist who stated "this species differs from 

 the probably closely related C. utahense chiefly 

 in its smaller and apparently much fewer-flowered 

 heads, and more northern and more montane 

 distribution. Further study may show the two to 

 be conspecif ic" (Hitchcock et al. 1955) . 



Moore and Frankton (1963) suggested that C. 

 pulcherrimum and C. subniveum were perhaps 

 conspecif ic, but were uncertain because of the 

 advanced maturity and insect damage of the type 

 specimen of C. subniveum . Gardner (1974) however, 

 refutes this idea with morphological data from a 

 study of the isotypes at Rocky Mountain herbarium, 

 and karyological and chemical data from field 

 collections. 



