Rydberg: Studies on the Rocky Mountain Flora 633 



I 



Plant sparingly and loosely floccose ; leaves glabrate in age. 



I. H. tenuifolius. 

 Plant densely tomentose ; leaves permanently tomentose. 



* 



Stem less than 3 dm. high. 



2. H. tomentosus. 



Stem-leaves much reduced; stem white-tomentose or nearly so ; heads 



few. 



3. H. s capos 2 is. 



Stem-leaves not much reduced ; stem sparingly grayish tomentose 



5- H- cine reus. 

 Pappus 1 mm. or less long, shorter than the corolla-tube ; stem-leaves and heads 



few. 



Pappus not hidden by the hairs of the achenes. 



Stem permanently densely white-tomentose ; achenes silky. 



4. //. arenosus. 

 Stem sparingly grayish tomentose, glabrate in age ; achenes loosely villous 



5. H. cinereus. 

 Pappus hidden by the hairs of the achenes, or sometimes none. 



Leaflets glabrate in age, at least above ; ultimate segment 5-30 mm. 



long. 



6. H.filifo litis. 



Leaves permanently densely white-tomentose ; ultimate segments short, 

 1-5 mm. long. 7. H. luteus. 



Throat of the corolla 3-4 mm. long, 3-4 times as long as the lobes. 8. H. macroglottis. 



I. Hymenopappus tenuifolius Pursh, Fl. Am. Sept. 742. 18 14 



This is generally described as a biennial ; occasionally the 

 root is of a longer duration and the plant becomes a short- 

 lived perennial and then hard to distinguish from a large specimen 

 of H. filifolius except by the pappus. H. tenuifolius grows on 

 prairies, from Nebraska and Wyoming to Texas. 



2. Hymenopappus tomentosus sp. nov. 



A densely and permanently white-tomentose plant, apparently 

 biennial. Stem 3-4 dm. high, leafy and branched above: leaves 

 5-7 cm. long, bi-pinnately divided into linear segments, 4-10 mm. 

 long, about 1 mm. wide : heads many, corymbose-paniculate, about 

 8 mm. high and broad ; involucre densely woolly, somewhat tur- 

 binate : flowers yellow: corolla tube and throat each a little over 

 I mm. long; the latter broadly campanulate, of about the same 

 length as the lobes ; achenes silky strigose ; scales of the pappus 

 a little shorter than the corolla-tube. 



Nearest related to the preceding, this species is easily distin- 

 guished by the dense permanent tomentum and the yellow flowers. 



Utah: St. George, 1877, Dr. E. Palmer, 270 (type in the 

 Columbia Herbarium). 



