HOSACEAE (ROSE FAMILY) 



Key to the Sections * 



Short-lived plants, mostly biennials ...... I. SUPINAE. 



Perennials. 



Leaves digitately 5-9-foliolate. 



Petioles witnout a remote reduced pair of leaflets; terminal 

 leaflet not petiolulate. 



Depressed spreading perennials II. CONCINNAE. 



Erect perennials, 1-several dm. high ... . . III. GRACILES. 

 Petioles with a remote reduced pair of leaflets or the termi- 

 nal leaflet petiolulate IV. SUBJUGAE. 



Leaves digitately 3-foliolate V. NIVEAE. 



Leaves pinnate. 



Style short, not longer than the mature achene, glandular- 

 thickened below VI. MULTIFIDAE. 



Styles long, exceeding the mature achene, filiform. 



Leaflets 3-7 VII. RUBRICAULES. 



Leaflets 7-27. 



Green or greenish, never tomentose . , VIII. MULTIJUGAE. 

 Whitish-silKy or tomentose IX. LEUCOPHYLLAE. 



I. SUPINAE. Short-lived plants, mostly biennials; style short, 



thickened-glandular below. 

 Leaves all pinnately 5- or more-foliolate; achenes with a lateral 



gibbosity . . . . . . ... . . 1. P. paradoza. 



Some or all of the leaves trifoliolate. 



Upper leaves trifoliolate; the lower pinnate. 



Achenes with a lateral gibbosity; flowers axillary . . 2. 

 Achenes not gibbous; flowers in a leafy cyme ... 3. 

 All the leaves trifoliolate. 



Stamens 10 or fewer; sepals exceeding the petals. 



Leaflets cuneate; flowers in a broadly branched cyme . 4. 



Leaflets broadly obovate; flowers in"racemose cymules . 5. 



Stamens more than 10; sepals and petals subequal - . .6. 



II. CONCINNAE. Depressed-spreading perennials, digitately 5- 



foliolate; style short-filiform. 



Leaflets more or less deeply toothed all around .... 7. 

 Leaflets truncately 3-5-toothed at apex ..... 8. 



III. GRACILES. More or less erect perennials, digitately 5-9- 

 foliolate; style long and filiform. 



Leaflets toothed or cleft halfway to the midrib, or less. 

 Leaves without white-tomentum. * 



Densely silky-villous at least below. 

 Tall erect plants, 3 or more dm. high. 



Cyme glomerate-congested, almost capitate ... 9. 

 Cyme corymbosely broad-topped ..... 10. 

 Low suberect plants, usually less than 3 dm. high . . 11. 

 Sparsely pubescent or glabrate, green. 



Low, subglaucous, sparsely villous plants, usually less than 



3 dm. high. 

 Leaflets subpinnate and somewhat decurrent . . 12. 



Leaflets strictly digitate 13. 



Tall, dark green, more or less hirsute plants, 3 dm. or more 



high 14. 



Leaves white-tomentose. 



15. 

 16. 



Below only, green above . . 



On both sides 



Leaflets toothed or cleft more than halfway to the midrib. 



Silky-sericeous; cyme crowded ...... 17. 



White-tomentose below; cyme open and broad-topped . 18. 



IV. SUBJUGAE. Rather low suberect perennials, having digitate 

 leaves with a pinnate tendency; style filiform. 



Leaves digitately 5-foliolate, with a small additional pair on the 



petiole 19. 



Leaves digitately 5-foliolate, the terminal leaflet petiolulate . 20. 



V. NIVEAE. Low tufted perennials, digitately trifoliolate; style 



usually glandular-thickened near the base. 



Stem several-flowered; leaflets oblong-cuneate .... 21. 

 Stem 1-3-flowered; leaflets broadly obovate-rhomboid . . 22. 



VI. MULTIFIDAE. Erect perennials; leaves pinnately 5-15- 

 foliolate; style glandular-thickened toward the base. 



Leaves silvery-white on both sides . . . . . . 23. 



Leaves not silvery-white, at least not above. 



Leaves silky-villous or subtomentose 24. 



Leaves neither silky-villous nor tomentose. 



Somewhat hirsute, dark green on both sides . . . 25. 

 Obscurely pubescent and granulo-glandular . . 26. 



P. Nicollettii. 

 P. rivalis. 



P. leucocarpa. 



P. biennis. 



P. monspeliensis. 



P. concinna. 

 P. bicrenata. 



P. glomerata. 

 P. viridescens. 

 P. diversifolia. 



P. decurrens. 

 P. glaucophylla. 



P. Nuttallii. 



P. gracilis. 

 P. Candida. 



P. pectinisecta. 

 P. flabelliformis. 



P. subjuga. 



P. quinquefolia. 



P. nivea. 

 P. uniflora. 



P. pinnatifida. 

 P. pennsylvanica. 



P. atrovirens. 

 P. virgulata. 



* Adapted from Dr. P. A. Rydberg's Monograph of the genus, 

 exhaustive work is gratefully acknowledged. A. N. 



Indebtedness to that 



