Herbs, annual, winter annual, or perennial, sometimes mat-forming. Taproots filiform to stout and woody, perennial plants often with branched caudex or with rhizomes or trailing stems. Stems ascending to erect or prostrate, simple or branched, ± terete. Leaves mostly connate proximally, petiolate (M. cumberlandensis, M. godfreyi proximal leaves) or sessile; blade 1–3-veined, sometimes obscurely so, filiform-linear to subulate, lanceolate or oblanceolate, rarely to ovate, herbaceous to succulent, apex blunt, rounded, or obtuse to acute, acuminate, or spinescent. Inflorescences terminal, open or seldom congested cymes or flowers solitary and terminal or axillary, rarely absent; bracts paired, herbaceous or scarious, rarely absent (M. pusilla, M. rossii). Pedicels erect to arcuate-spreading, rarely reflexed (M. drummondii) in fruit. Flowers: perianth and androecium perigynous; hypanthium usually disc-, occasionally dish- or cup-shaped; sepals 5, distinct, green (herbaceous portion purple in M. arctica, M. macrocarpa, and M. rossii), linear, lanceolate, or oblong to elliptic, ovate, or broadly ovate, 1.5–6(–9) mm, margins herbaceous or silvery and scarious, apex rounded or obtuse to acute, acuminate, or spinescent, sometimes hooded; petals 5 or rarely absent, white, rarely pink (M. biflora) or lilac (M. marcescens), clawed (M. glabra, M. groenlandica) or not, blade apex entire, emarginate, or notched; nectaries 5, at base of filaments opposite sepals, sometimes prominent and 2-lobed; stamens 10 (8–10 in M. godfreyi), arising from hypanthium; filaments distinct; staminodes absent; styles 3 (to 4 in M. cumberlandensis, M. godfreyi), filiform, 0.6–2.5 mm, glabrous proximally; stigmas 3 (to 4 in M. cumberlandensis, M. godfreyi), linear along adaxial surface of styles, minutely papillate (30×). Capsules ovoid to broadly ellipsoid or rarely globose, opening by 3 incurved or erect to recurved valves; carpophore absent or sometimes present. Seeds 1–25, reddish brown to brown or black (or rarely yellowish or purplish brown), spherical or suborbiculate to reniform or obliquely triangular, plump or variously compressed, smooth, reticulate, tuberculate, muriculate-papillate, or rarely with long marginal papillae (M. macrocarpa), marginal wing absent (present in M. douglasii), appendage absent. x = 7, 9, 10, 12, 13, 14, 15, 23.

Distribution

Temperate and arctic Northern Hemisphere, n Africa, Asia Minor.

Discussion

Species ca. 175 (33 in the flora).

The nectaries in Minuartia flowers are often enlarged (to 0.5 mm) and variously lobed; they may not be apparent in fruiting material, possibly due to resorption by the developing flower following pollination. The hypanthium varies from disc- to cup-shaped and ranges in size from less than 1 mm to 3 to 4 mm in diameter (measured on the curve if cup-shaped). The cup-shaped hypanthium is best developed in fruiting material of M. arctica, M. obtusiloba, and relatives.

Minuartia is the second largest genus of Caryophyllaceae in our flora. It is the largest that here includes strictly native taxa. Of the eight genera with ten or more species, only Eremogone also is represented solely by native species.

J. McNeill (1962) outlined an infrageneric classification of Minuartia that included four subgenera and 12 sections within subg. Minuartia; our 33 species would be distributed among seven of those 12 sections. While we follow McNeill (1962, 1980b) in recognizing Arenaria and Minuartia, we have chosen not to adopt his hierarchy formally. Some of his groups do appear to represent natural assemblages; others do not. One of the latter includes most of the Minuartia species native to the southeastern United States. McNeill (1962) placed these species in sect. Uninerviae (Fenzl) Mattfeld; J. Mattfeld (1922) divided them among three series within that section; Á. Löve and D. Löve (1975) segregated two species as the genus Porsildia. There has been no thorough subsequent study of the entire group that could further resolve the question. Molecular investigation of Minuartia (M. Nepokroeff et al. 2001) suggested that it is not monophyletic. One or more of the various segregate genera that have been proposed, originally based on morphological features, with some resurrected by Löve and Löve on cytological grounds, and that are now in use (e.g., Alsinanthe, Alsinopsis, Lidia, Minuopsis, Tryphane; W. A. Weber and R. C. Wittmann 1992) may prove to be supported by dna analysis as well.

Minuartia rossii, a densely pulvinate plant of moist arctic areas, may be difficult to identify in the key since flowers are often absent, especially in northern populations. Vegetative reproduction via easily detached axillary fascicles in the upper leaf axils is more common in these plants.

Selected References

Cormick, J. F., J. R. Bozeman, and S. A. Spongberg. 1971. A taxonomic revision of granite outcrop species of Minuartia (Arenaria). Brittonia 23: 149–160.

Mattfeld, J. 1922. Geographisch-genetische Untersuchungen über die Gattung Minuartia (L.) Hiern. Repert. Spec. Nov. Regni Veg. Beih. 15. Mc

McNeill, J. and I. J. Bassett. 1974. Pollen morphology and the infrageneric classification of Minuartia (Caryophyllaceae). Canad. J. Bot. 52: 1225–1231.

Lower Taxa

Minuartia arctica, Minuartia austromontana, Minuartia biflora, Minuartia californica, Minuartia caroliniana, Minuartia cismontana, Minuartia cumberlandensis, Minuartia dawsonensis, Minuartia decumbens, Minuartia douglasii, Minuartia drummondii, Minuartia elegans, Minuartia glabra, Minuartia godfreyi, Minuartia groenlandica, Minuartia howellii, Minuartia macrantha, Minuartia macrocarpa, Minuartia marcescens, Minuartia michauxii, Minuartia muscorum, Minuartia nuttallii, Minuartia obtusiloba, Minuartia patula, Minuartia pusilla, Minuartia rosei, Minuartia rossii, Minuartia rubella, Minuartia stolonifera, Minuartia stricta, Minuartia tenella, Minuartia uniflora, Minuartia yukonensis

Key

1	Plants annual, not cespitose, rarely mat-forming	> 2
1	Plants perennial, often cespitose, pulvinate, or mat-forming	> 17
2	Sepal apices obtuse or merely acutish	> 3
2	Sepal apices acuminate to distinctly acute	> 8
3	Pedicels stipitate-glandular	> 4
3	Pedicels glabrous	> 6
4	Sepals 1-3-veined; seeds compressed, winged	Minuartia douglasii
4	Sepals obscurely veined; seeds somewhat compressed, not winged	> 5
5	Leaf blades glabrous; seeds 0.7-0.8 mm, orbiculate, echinate; sc United States	Minuartia drummondii
5	Leaf blades stipitate-glandular; seeds 1.4-1.7 mm, suborbiculate, low-tuberculate; California, Oregon	Minuartia howellii
6	Sepals 1- or 3-veined, 2.5-2.8 mm; petals not clawed; California, Oregon	Minuartia californica
6	Sepals obscurely veined, 1.5-4 mm; petals clawed or not; e United States	> 7
7	Petals broadly obovate, clawed; seeds 0.5-0.8 mm, obliquely triangular with adaxial groove	Minuartia glabra
7	Petals oblanceolate to spatulate, not clawed; seeds 0.4-0.6 mm, suborbiculate, not grooved	Minuartia uniflora
8	Sepals obscurely veined; leaves stipitate-glandular	Minuartia howellii
8	Sepals 1-5-veined, often prominently so; leaves glabrous or seldom stipitate-glandular	> 9
9	Pedicels glabrous	> 10
9	Pedicels stipitate-glandular, sometimes sparsely so	> 13
10	Leaves obscurely veined; petals 0.5-1 times as long as sepals or absent	Minuartia pusilla
10	Leaves 1-3-veined; petals 1-2.2(-3) times as long as sepals	> 11
11	Leaves weakly 1-veined abaxially; sepals 1- or 3-veined, apex rounded to acute	Minuartia californica
11	Leaves 1-veined abaxially; sepals prominently 3-5-veined, apex acute to acuminate	> 12
12	Sepals 3(-5)-veined; petals 1-1.5 times as long as sepals; capsules equaling or longer than sepals; California, Oregon	Minuartia cismontana
12	Sepals (3-)5-veined; petals 1.5-2.2(-3) times as long as sepals; capsules usually shorter than sepals; se and c United States	Minuartia patula
13	Petal apices entire, w United States	> 14
13	Petal apices emarginate or notched; se and c United States	> 15
14	Seeds 1.3-2 mm, winged	Minuartia douglasii
14	Seeds 0.4-0.6 mm, not winged	Minuartia tenella
15	Flowering stems arising from slender wintering stems; inflorescences 3-5(-7)-flowered; petals oblong-spatulate	Minuartia godfreyi
15	Wintering stems absent; inflorescences 5-50+-flowered; petals obovate	> 16
16	Sepals 3-veined, apex acute; leaf blades linear-lanceolate to oblanceolate, (0.6-)1.5-3.2 mm wide; seeds black, muriculate-papillate	Minuartia muscorum
16	Sepals (3- or) 5-veined, apex acute or acuminate; leaf blades linear, 0.5-1.5(-1.8) mm wide; seeds reddish brown to black, tuberculate	Minuartia patula
17	Sepal apices broadly obtuse or rounded	> 18
17	Sepal apices acute to acuminate or spinescent	> 31
18	Stems pubescent, at least distally, often stipitate-glandular	> 19
18	Stems glabrous	> 24
19	Leaf blade apices acuminate-pungent; stems 10-30 cm; inflorescences 3-13-flowered	Minuartia yukonensis
19	Leaf blade apices rounded to truncate; stems 1-12 cm; inflorescences 1-5-flowered	> 20
20	Leaf blades flat, obscurely 1- or 3-veined	> 21
20	Leaf blades 3-angled or rounded 3-angled, obscurely or prominently 1- or 3-veined	> 22
21	Inflorescences with flowers solitary; capsules narrowly ellipsoid, 10-18 mm; seeds ringed with elongate papillae	Minuartia macrocarpa
21	Inflorescences 3-5-flowered; capsules broadly ellipsoid, 5.5 mm; seeds smooth or obscurely sculptured	Minuartia biflora
22	Axillary leaves absent; leaf blades obscurely 1-veined; seeds 1.2-1.6 mm, brown, minutely tuberculate	Minuartia arctica
22	Axillary leaves present among vegetative leaves; leaf blades 1- or 3-veined abaxially; seeds 0.6-1.2 mm, brown or reddish tan, smooth or obscurely sculptured	> 23
23	Capsules 6-10 mm; seeds 0.9-1.2 mm, brown	Minuartia marcescens
23	Capsules 3.5-6 mm; seeds 0.6-0.7 mm, reddish tan	Minuartia obtusiloba
24	Stems 8-28 cm; inflorescences 5-12+-flowered; sepals broadly ovate	Minuartia caroliniana
24	Stems 1-10(-20) cm; inflorescences 1-5-flowered; sepals linear to ovate or obovate	> 25
25	Petals with apex emarginate or notched, petals 1.4-2.2 times as long as sepals; inflorescences 2-5(-7)-flowered cymes or flowers solitary	> 26
25	Petals with apex entire, petals 0.8-2 times as long as sepals (sometimes absent); inflorescences with flowers solitary	> 28
26	Pedicels stipitate-glandular	Minuartia biflora
26	Pedicels glabrous	> 27
27	Leaf blades (10-)20-30(-40) × 1-3 mm, linear-oblanceolate to linear-spatulate; inflorescences 1(-3)-flowered	Minuartia cumberlandensis
27	Leaf blades 4-12(-15) × 0.5 mm, ± linear; inflorescences 3-5-flowered	Minuartia groenlandica
28	Leaf blades 3-veined, often prominently so abaxially; capsules narrowly ellipsoid, 10-18 mm	Minuartia macrocarpa
28	Leaf blades 1-veined; capsules spherical or ellipsoid, 1.5-4 mm	> 29
29	Stems 1-3 cm; sepals 1-veined	Minuartia rossii
29	Stems 3-15 cm; sepals 3-veined	> 30
30	Sepals, linear to lanceolate; petals rudimentary or absent	Minuartia austromontana
30	Sepals, ovate to lanceolate; petals 0.8-1 times as long as sepals	Minuartia elegans
31	Petals 2.5-3 times as long as sepals, apex shallowly notched	Minuartia godfreyi
31	Petals with apex entire, if slightly emarginate, then petals 0.7-0.9 times as long as sepals, or absent	> 32
32	Pedicels stipitate-glandular	> 33
32	Pedicels glabrous	> 37
33	Stems cespitose to mat-forming; taproot not woody, filiform to somewhat thickened, rhizomes or trailing stems absent; seeds 0.4-0.5 mm	Minuartia rubella
33	Stems mat-forming; taproot woody, stout; rhizomes, stolons, or trailing stems present; seeds 1.5-2.7 mm	> 34
34	Plants densely stipitate-glandular throughout; w North America	Minuartia nuttallii
34	Plants sparsely stipitate-glandular on pedicels and sepals; California	> 35
35	Petals 0.7-0.9 times as long as sepals; stems and leaves green	Minuartia decumbens
35	Petals 1.4-2.2 times as long as sepals; stems and leaves glaucous or gray-green	> 36
36	Stems and leaves glaucous, proximal leaves longer than internodes	Minuartia rosei
36	Stems and leaves gray-green, proximal leaves often shorter than internodes	Minuartia stolonifera
37	Petals 1.1-2 times as long as sepals	> 38
37	Petals 0.5-1 times as long as sepals, rudimentary or absent	> 40
38	Leaf blades 1-4 mm, 3-angled, 1-veined; sepals 1-veined; high arctic	Minuartia rossii
38	Leaf blades 5-30 mm, flat to 3-angled, 1-3 veined; sepals 3-veined	> 39
39	Leaf blades flat to navicular, apex blunt to pungent; inflorescences 5-30-flowered; Great Plains and east	Minuartia michauxii
39	Leaf blades navicular, apex rounded; inflorescences 1- or 2-5(-8)-flowered; Great Basin and Rocky Mountains	Minuartia macrantha
40	Inflorescences with flowers solitary, terminal	> 41
40	Inflorescences with flowers solitary and terminal or often 2-5(-15)-flowered	> 42
41	Sepals linear to lanceolate; petals rudimentary or absent	Minuartia austromontana
41	Sepals ovate to lanceolate; petals 0.8-1 times as long as sepals	Minuartia elegans
42	Sepals 3.5-5 mm, to 5.5 mm in fruit; seeds 0.7-1 mm	Minuartia macrantha
42	Sepals (1.5-)2.5-3.2 mm, to 4 mm in fruit; seeds 0.4-0.6 mm. [43. Shifted to left margin.—Ed.]	> 43
43	Inflorescences 7-15-flowered (rarely fewer); seeds dark brown to black, 0.5-0.6 mm	Minuartia dawsonensis
43	Inflorescences 1-3(-5)-flowered; seeds brown or reddish brown, 0.4-0.6 mm	Minuartia stricta