‘Part 4, 1908] ROSACEAE 305 
equaling the sepals; stamens 10-15; pistils numerous; styles terminal, fusiform; achenes 
smooth, with a thick corky swelling on the inner side. 
TYPE LOCALITY : Devil’s Lake [North Dakota]. 
DISTRIBUTION : North Dakota to Missouri and Kansas. 
ILLUSTRATIONS: Britt. & Brown, Ill. Fl. f. 1926; Mem. Dep. Bot. Columbia Univ. 2: pL. 6. 
10. Potentilla rivalis Nutt.; T. & G. Fl. N. Am. 1: 437. 1840. 
Tridophyllum rivale Greene, Leaflets 1: 189. 1905. 
Stem erect and simple, branched above, often tinged with brown or purple, finely vil- 
lous-hirsute, leafy; stipules broadly ovate, 1-2 cm. long, often coarsely toothed; lower 
leaves pinnate with two pairs of approximate leaflets, the upper trifoliolate, sometimes all tri- 
foliolate ; leaflets 2-5 cm. long, obovate, with coarse ovate teeth; cyme leafy, with ascend- 
ing branches; flowers on short pedicels, less than 5 mm. in diameter; hypanthium hirsute, 
in age about 5 mm. in diameter; bractlets oblong, obtuse or acute, about 3 mm. long, 
rather shorter than the ovate acute sepals; petals cuneate, much shorter than the sepals; 
stamens about 10; pistils numerous; styles terminal, fusiform; achenes smooth. 
TYPE LOCALITY : Alluvial soil along Lewis River [Snake River]. 
DISTRIBUTION : River valleys from British Columbia to Saskatchewan and Mexico. 
ILLUSTRATIONS: Lehm. Rev. Potent. #/. 61, Mem. Dep. Bot. Columbia Univ. 2: 1. 7. 
11. Potentilla millegrana Engelm.; Lehm. Delect. Sem. Hort. 
Hamb. 1849: 11. 1849. 
Potentilla rivalis millegrana S, Wats. Proc. Am. Acad. 8: 553. 1873. 
Poteniilia Nicollet Sheldon, Minn. Bot. Stud. 1: 16, in part. 1894. Not P. supina Nicol- 
letti S. Wats. 1873. . 
Potentilla leucocarpa Rydb. in Britt. & Brown, Ii]. Fl. 2: 212. 1897. 
Stem slender and branched throughout, 4-8 cm. high, divaricate, softly pubescent, 
sometimes nearly glabrous; stipules lanceolate or oval, generally subentire, acute, 3-10 mm. 
long; leaves ternate, finely pubescent, generally somewhat pale and thin; petioles of the 
lower leaves 3-8 cm. long; leaflets oblong-cuneate, deeply serrate, 1-6 cm. long, the middle 
one often petiolulate ; cyme much branched, spreading, leafy, but the leaves much reduced ; 
flowers 3-4 mm. in diameter, on slender pedicels; hypanthium soft-pubescent, in fruit 
about 5 mm. in diameter; bractiets and sepals oblong-ovate, acute, about the same length, 
but the former a little narrower, 3-4 mm. long; petals oblong-cuneate, about half as long 
as the sepals, light-yellow; stamens generally 10, with didymous anthers ; pistils numerous ; 
styles terminal, fusiform; achenes smooth, light-colored, small. 
TYPE LOCALITY : [St. Louis, Missouri,] North America, ; . . 
DISTRIBUTION: River valleys, from Ulinois to Manitoba, Washington, California, and New 
Mexico. . 
ILLUSTRATIONS: Britt. & Brown, Ill. Fl. f. 1924; Mem. Dep. Bot. Columbia Univ. 2: pi. 8. 
12. Potentilla michoacana Rydb. Mem. Dep. Bot. Columbia 
Univ. 2: 44. 1898. 
Spreading from an annual root, finely pubescent, divergently branched ; leaves ternate 
with shortly stalked terminal leaflets; leaflets narrowly cuneate, few-toothed above the 
middle, 1-2 cm. long, finely puberulent; bractlets oblong, about equaling the broadly 
ovate sepals; petals white, obovate, truncate, half the length of the sepals; stamens 5. 
TYPE LOCALITY: State of Michoacan, Mexico. _ 
DISTRIBUTION : Known only from the type locality. 
13. Potentilla biennis Greene, Fl. Fran. 1: 65. 1891. 
Potentilla millegrana S. Wats. Bot. King’s Expl. 85, in part. 1871. Not P. millegrana Engelm. 
1849. 
Potentilla lateriflora Rydb. Bull. Torrey Club 23: 261, 1896. 
Potentilla millegrana lateriflora Engelm.; Rydb. Bull. Torrey Club 23: 261, as synonym, 1896. 
Tridophyllum bienne Greene, Leaflets 1: 189. 1905. 
Annual or biennial ; stems often several from the root, 3-5 dm. high, terete, finely and 
rather densely pubescent and more or less glandular, often tinged with red or purple, simpler 
