Herbs, with alternate stipulate digitately or pinnately compound leaves, and cymose or solitary yellow, white or purple perfect flowers. Calyx-persistent, its tube concave or hemispheric, 5-bracteolate (rarely 4-bracteolate), 5-lobed (rarely 4-lobed). Petals 5 or rarely 4, mostly obovate or orbicular, usually emarginate. Stamens 00, seldom 5 or 10; filaments slender; anthers small. Carpels numerous, inserted on a dry, usually pubescent receptacle; style terminal or nearly so, deciduous. Seed pendulous, anatropous. [Diminutive of potens, powerful, from the medicinal properties of some species.]

Over 300 species, nearly all of them natives of the north temperate zone. Besides the following at least 100 others occur in the western and northwestern parts of North America and several in Arctic America. Type species: Potentilla reptans L.

A. Flowers solitary, axillary, long-peduncled.

Flowers 4-parted; upper leaves 3-foliolate.

1.

P. procumbens.

Flowers 5-parted; leaves usually all 5-foliolate (genus Callionia Greene).

Pubescence of the stem, petioles and peduncles appressed.

Leaflets sparingly silky beneath, dentate nearly to the base.

2.

P. simplex.

Leaflets densely silky beneath, dentate only above the middle.

3.

P. pumila.

Pubescence of the stem, petioles and peduncles spreading.

4.

P. canadensis.

B. Flowers cymose.

a. Cymes very leafy, several-many-flowered, the flowers or some of them apparently axillary.

Mainly annuals or biennials; style fusiform, glandular at the base.

Achenes corky-gibbous.

Leaves all pinnate; inflorescence evidently cymose.

5.

P. paradoxa.

Upper leaves ternate; inflorescence falsely racemose.

6.

P. Nicolletii.

Achenes not gibbous.

Leaves all ternate; stamens 10-20.

Petals about half as long as the calyx-lobes; calyx-tube 2"-21/2" broad in fruit.

7.

P. millegrana.

Petals more than half as long as the calyx-lobes; calyx-tube 3 1/2" broad in fruit.

8.

P. monspeliensis.

Basal leaves apparently 5-foliolate; stamens 5.

9.

P. pentandra.

Perennials; style filiform, not glandular.

Leaves white-tomentose beneath.

10.

P. argentea.

Leaves grayish silky beneath.

11.

P. intermedia.

b. Cymes not very leafy, usually few-flowered.

Leaves digitately divided.

Basal leaves 5-9-foliolate.

Plant tall, 1° high or more; introduced.

12.

P. recta.

Plants low, less than 8' high; native boreal species.

13.

P. tnaculata.

Basal leaves 3-foliolate; boreal and alpine species.

Leaves densely white-pubescent beneath.

14.

P. nivea.

Leaves green beneath, not densely pubescent.

Petals much exceeding the calyx-lobes.

15.

P. emarginata.

Petals scarcely exceeding the calyx-lobes.

16.

P. Robbinsiana.

Leaves pinnately divided.

Style longer than the ripe achene, filiform; leaflets toothed.

Bractlets much shorter than the acuminate calyx-lobes.

17.

P. effusa.

Bractlets at least three-fourths as long as the acute calyx-lobes.

18.

P. Hippiana.

Style not longer than the ripe achene; leaflets incised.

Style not thickened at the base; boreal species.

19.

P. multifida.

Style thickened and glandular at the base.

Leaves white-tomentose beneath.

20.

P. bipinnatifida.

Leaves grayish pubescent beneath.

Leaflets approximate, the leaves suborbicular or pentagonal in outline.

21.

P. pectinata.

Leaflets distant, the leaves obovate in outline.

22.

P. pennsylvanica.