ROSE FAMILY 411 



IX. NlVEAE. 



Leaflets oblanceolate or obovate, toothed or cleft, except at the very base; stem usually 



1-2 dm. high, more or less leafy, several-flowered. 

 Leaflets deeply cleft, the clefts extending at least half-way to the midrib. 



Inflorescence dense and congested. 41. P. Hookeriana. 



Inflorescence open, with slender pedicels. 39. P. quinquefolia. 



Leaflets coarsely toothed, the toothing rarely extending half-way to the midrib. 



42. P. nivea. 



Leaflets broadly cuneate, toothed only above the middle; stems usually lss than 1 dm 

 high, scapiform, 1-2-flowered (rarely 3-flowered). 43. P. uniflora. 



X. FRIGIDAE. 



Stem less than 1 dm. high, decumbent; leaflets obovate, short-pilose; petals 5-8 mm. 



long. 44. p. emarginata. 



Stem 1-3 dm. high, erect; leaflets cuneate, flabelliform; petals 8-10 mm. long. 



45. P. flabellifolia. 

 XI. BREVIFOLJAE. 

 One species. 46. P. brevifolia. 



XII. RUBRICAULES. 



Leaves mostly greenish above, tomentose beneath. 



Segments of the leaves linear; stem nearly erect, slender; sepal almost linear. 



47. P. tenerrima. 



Segments of the leaves lanceolate or oblong; sepals lanceolate. 

 Plant densely cespitose; segments of the leaves obtuse. 



Segments lanceolate, acute; leaflets only slightly tomentose beneath. 



61. P. viridior. 

 Segments oblong to orbicular, obtuse. 



Segments of the leaves narrowly oblong. 48. P. saximontana. 



Segments of the leaves oval to orbicular. 49. P. minutifoHa. 



Plant with spreading branches ; segments of the leaves acute. 



38. P. divisa. 

 Leaves densely silky on both sides. 



Leaves with 2 or 3 pairs of leaflets; bractlets much shorter than the sepals; stem 



strict. 50. P. filicaulis. 



Leaves with 3-5 pairs of leaflets ; bractlets little if at all shorter than the sepals ; stem 



decumbent-ascending . 



Leaflets deeply cleft. 51. P. Macounii. 



Leaflets merely toothed. 52. P. proximo,. 



XIII. LEUCOPHYLLAE. 



Pistils 20 or fewer; bractlets much shorter than the acuminate sepals; tomentum if any 



loose and not dense. 



Plant tomentose throughout. 53. P. coloradensis. 



Plant green and nearly glabrous up to the inflorescence. 54. P. rupincola. 



Pistils usually more than 20. 



Leaves white-tomentose beneath; pubescence of the stem and petioles mostly ap- 



pressed. 



Leaves almost equally white-pubescent on both sides. 

 Bractlets much shorter than the acuminate sepals. 



Leaflets not closely approximate, finely tomentose. 55. P. effusa. 



Leaflets closely approximate, coarsely appressed-silky as well as tomentose. 



56. P. lupina. 

 Bractlets at least three-fourths as long as the acute sepals. 



Inflorescence open; leaves silky and shining. 57. P. Hippiana. 



Inflorescence dense; leaves loosely tomentose and rather dull. 



58. P. argyrea. 

 Leaves green and merely silky above. 



Leaflets usually 9, all usually ascending, the upper pair decurrent. 



59. P. propinqua. 

 Leaflets 5-7, the lower spreading or reflexed, the upper pair not decurrent. 



Leaflets densely white beneath; teeth ovate. 60. P. pulcherrima. 



Leaflets thin, sparingly tomentose beneath; teeth lanceolate. 



61. P. viridior. 



Leaves green beneath, only slightly tomentulose when young; pubescence of the 

 stems and petioles spreading. 62. P. ambigens. 



XIV. MULTIJUGAE. 



Pedicels at least in fruit arcuate-spreading; stems usually diffuse or spreading; leaflets 

 pinnately divided, with several or many, oblong or lanceolate divisions. 



63. P. plattensis. 

 Pedicels erect or ascending, straight; stem erect or ascending. 



Leaflets dissected to near the midrib. 



Stem and mature leaves glabrate: leaflets cuneate, cleft above the middle into 



oblong or ovate divisions. 

 Stem 1-3 dm. high ; leaflets elongate-cuneate, with oblong divisions. 



64. P. Nelsoniana. 

 Stem about 1 dm. high; leaflets short-cuneate, merely toothed at the apex. 



65. P. decurrens. 



