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Key to families | Table of families and genera




Michael S. Park

Plant generally ± hairy, often glandular; caudex or rhizome generally not woody, generally scaly. Leaf: basal (cauline); blade linear to (ob)ovate or ± round, base tapered to reniform, margin entire or toothed. Inflorescence: flowers few to many; bracts scale-like. Flower: generally radial; hypanthium free or ± fused to ovary; petals 5, white, sometimes with yellow spots at base; stamens 10, filaments flat or variously inflated; pistils 1 (chambers 2, placentas 2, axile or occasionally proximally axile and distally marginal) or 2, ovary superior to ± inferior (sometimes more superior in fruit), styles free throughout. Fruit: capsule or 2 follicles.
± 80 species: North America, Eurasia, South America, especially cool temperate northern hemisphere. (Latin: small flower) [Elvander 1984 Syst Bot Monogr 3:1–44] Intermediates common between Micranthes integrifolia, Micranthes nidifica, Micranthes fragosa, Micranthes aprica; some may be vegetatively reproducing, sterile hybrids. Study needed.
Unabridged references: [Small & Rydberg 1905 N Am Fl 22:132–150]

Key to Micranthes

1. Leaves cauline on ± trailing stem — blade entire; flowers in head-like cluster ..... M. tolmiei

1' Leaves basal (bracts occasionally leaf-like)

2. Proximal flowers replaced by bulblets; flowers ± bilateral, 3 petals broader than other 2

3. Base of all petals ± 2-spotted; leaf blade linear-elliptic, margin ± entire or with minute teeth distally ..... M. bryophora

3' Base of only 3 broad petals (rarely all) ± 2-spotted; leaf blade obovate, teeth generally coarse ..... M. ferruginea

2' Inflorescence bulblets 0; flowers radial, petals ± equal

4. Filaments inflated distally; petal spots 2

5. Leaf blade ovate to elliptic, base truncate to tapered; ovaries fused only at base ..... M. marshallii

5' Leaf blade ± round, base cordate to reniform; ovaries fused throughout — fruit tip purple, base yellow-banded ..... M. odontoloma

4' Filaments inflated proximally, or ± flat and not inflated; petal spots 0

6. Filaments inflated proximally; ovary superior in flower and fruit ..... M. howellii

6' Filaments not inflated proximally, ± flat, narrowed at tip; ovary ± inferior to 1/2-inferior in flower, superior in fruit

7. Plant generally > 4 dm; leaf blade linear to oblanceolate, generally > 10 cm, long-tapered to an indistinct petiole; bogs, marshes, lake margins ..... M. oregana

7' Plant <= 3.5 dm; leaf blade elliptic, obovate, ovate, or triangular, generally < 10 cm, short-tapered to a distinct petiole; not in bogs, marshes or lake margins

8. Leaf blade shallowly toothed; inflorescence ± open, often 1-sided; flowers not clustered to loosely clustered; anthers purple to red (orange); petals ± 2 × sepals; styles on fruit generally > 1.5 mm ..... M. californica

8' Leaf blade ± entire to minutely toothed; inflorescence not 1-sided; flowers loosely to densely clustered; anthers generally yellow to orange; petals < 1.7 × sepals; styles on fruit generally < 1 mm

9. Petals 1–2 mm; sepals ± reflexed ..... M. nidifica

9' Petals generally > 2 mm; sepals generally ± erect to spreading (except Micranthes fragosa)

10. Pedicels ± glabrous to sparsely glandular; generally 1 head-like cluster of flowers at tip of inflorescence, sometimes with 1 or 2 smaller clusters on nearby short lateral branches; moist, sandy and gravelly montane to subalpine habitats >= 1600 m elevation ..... M. aprica

10' Pedicels densely glandular; lateral branches of inflorescence many, each with a terminal cluster of flowers; moist meadows, rocky slopes and outcrops

11. Lateral branches of inflorescence spreading to ascending; inflorescence cluster at tip of main axis open to ± congested, hemispheric to ± flat-topped; sepals ± reflexed to spreading ..... M. fragosa

11' Lateral branches of inflorescence ascending to erect; inflorescence cluster at tip of main axis dense, conical to cylindric; sepals ± erect to ascending ..... M. integrifolia

