544 Rydberg : Rocky Mountain flora 



&" Garrett 6732 (type, in herb. N. Y. Bot. Gard.) ; apparently 

 also, Salt Lake City, August, 1880, M. E. Jones 1905, and the 

 same locality, Sept., 1905, A. 0. Garrett lyiS. 



Carduus olivescens sp. nov. 



Perennial; stem slender, somewhat tinged with purple, more or 

 less floccose, 4-8 dm. high, leafy; leaves linear in outline, 1-2 dm. 

 long, densely white-tomentose beneath, loosely floccose above, 

 deeply pinnatifid, with numerous lanceolate, often 2- or 3-cleft 

 lobes, ending in short yellow spines; heads few, peduncled, about 

 3 cm. high, 3-3.5 cm. wide; bracts slightly floccose on the margins, 

 light olive-colored, darker towards the apex, ending in yellow spines 

 2—4 mm. long, or the innermost with lance-linear, slightly twisted 

 yellowish tips; corollas straw-colored; pappus plumose; tips 

 slightly clavate. 



This species was first determined questionably as Carduus 

 Tracyi, to which it is not closely related, not having the con- 

 spicuous broad glutinous dorsal ridges or the broad bracts of that 

 species. In leaf-form it resembles somewhat C. piilcherrimus, 

 although the upper surface is more floccose, but otherwise it is 

 not close to that species. 



Utah: Aquarius Plateau, August 5, 1905, Rydberg & Carlton 

 7450 (type, in herb. N. Y. Bot. Gard.). 



Thistle hybrids are very common in Europe and even tertiary 

 hybrids have been reported. No attempt has been made in this 

 country to segregate or recognize hybrids in this genus. As a rule 

 specimens of thistles are not so common in herbaria as would be 

 expected, probably owing to the difficulty in collecting and pre- 

 paring them. 



Thistles are not uncommon in the Rocky Mountains, especially 

 in Colorado. No person has perhaps contributed more to the 

 knowledge of these plants of that state than Mr. George E. 

 Osterhout, of New Windsor, Colorado. He has described a few 

 species himself and others have been described from material 

 collected by him. There are still more forms recognized by him 

 and distributed under manuscript names, but which he has been 

 reluctant to describe. With the aid of the material sent me 

 by him, augmented by other specimens collected by Baker, Shear, 

 Clements, myself, and others, it has been possible to recognize 



