Cerastium alpinum
Cerastium
alpine chickweed, alpine mouse-ear chickweed, céraiste alpin
cerastium, chickweed, céraiste, mouse-ear chickweed
slender, perennial taxa often rhizomatous, rooting at nodes.
prostrate or ascending, tomentose (very rarely subglabrous), hairs white, translucent, long, soft, flexuous, some usually also short and glandular; flowering shoots ascending, 5–20 cm; small axillary tufts of leaves usually absent; nonflowering shoots ± prostrate, to 6 cm.
ascending to erect or decumbent, simple or branched, terete.
marcescent or not, sessile;
blade obovate or ovate to elliptic-oblanceolate, elliptic, or lanceolate, usually 10–18 × 5–7 mm, apex obtuse, pubescence as on stems.
basally connate, petiolate (basal in some species) or sessile (cauline);
blade 1–5-veined, linear or elliptic to broadly ovate, not succulent (except in C. bialynickii, C. regelii, and C. viride), apex acute to obtuse.
open, (1–)2–4-flowered cymes;
bracts lanceolate, acute, margins narrow, scarious, glandular-pubescent.
terminal, open or congested cymes, or flowers solitary, axillary (racemosely arranged in C. axillare);
bracts paired, foliaceous or reduced, herbaceous or often with scarious margins.
straight but often becoming angled at base and curved at apex, slender, 5–30 mm, often elongating to 3 or 4 times as long as sepals, pubescence usually dense, hairs both long, flexuous, multicellular, and short, glandular, viscid.
erect, sometimes reflexed or hooked at apex in fruit, or flowers sometimes subsessile (C. regelii).
sepals green, often violet tipped, narrowly elliptic-lanceolate, 7.5–10 mm, margins ± narrow, apex acute to obtuse, densely pubescent, hairs both long, eglandular and short, glandular;
petals 1–2 times as long as sepals, apex shallowly 2-fid;
stamens 10;
styles 5.
bisexual, occasionally unisexual and pistillate;
perianth and androecium hypogynous or weakly perigynous;
hypanthium minimal;
sepals (4–)5, distinct, green (red-tipped in C. glomeratum and C. pumilum, often violet-tipped in C. alpinum, purple in C. bialynickii, turning pale orange-brown in fruit in C. texanum), elliptic to ovate, 3–12 mm, herbaceous, margins translucent to purplish, scarious, apex acute, acuminate, or obtuse, not hooded;
petals (4–)5 or sometimes absent, white (purple tinged in C. pumilum and C. regelii), clawed, blade apex 2-fid 1/5–1/2 of length, notched, or emarginate;
nectaries at base of filaments opposite sepals;
stamens usually 10, sometimes 5 or 8, occasionally 4;
filaments distinct, inserted at base of ovary;
staminodes absent or 1–4 (via anther abortion), linear;
styles (3–)5(–6), clavate to filiform, 0.5–2 mm, glabrous proximally;
stigmas (3–)5(–6), subterminal to linear along adaxial surface of styles, roughened to papillate (30x).
cylindric, slightly curved, 12–16 mm, to 2 times as long as sepals;
teeth 10, erect, margins convolute.
oblong or cylindric, usually ± curved, opening by 10, or occasionally 6 or 8, erect or spreading, convolute or revolute teeth, longer than sepals;
carpophore absent.
dark brown, 1–1.4 mm diam., acutely tuberculate;
testa not inflated.
15–150+, orange to brown, angular-obovate, often with abaxial groove, laterally compressed, papillate-tuberculate, marginal wing absent, appendage absent.
= [9?, 13, 15] 17, 18, 19.
= 72, 108.
Cerastium alpinum
Cerastium
Subspecies 3+ (2 in the flora).
The Cerastium alpinum group of species is a difficult complex of intergrading taxa. E. Hultén (1956) considered this complex to be the result of worldwide introgression among the various taxa. Members of this group in North America include C. aleuticum, C. alpinum, C. arcticum, C. beeringianum, C. bialynickii, C. fischerianum, C. regelii, and C. terrae-novae. Cerastium alpinum itself is distinguished from all other members of the complex by its lanate pubescence, which consists of long, silvery, translucent, multicellular, flexuous, often tangled hairs; the more or less square base of the calyx; the convex margins of the sepals; and, in well-grown plants, the long, slender, divaricate pedicels.
In western North America, Cerastium alpinum is replaced by C. beeringianum, which has long, straight, strigose, somewhat fuscous hairs, usually smaller flowers, and smaller seeds. The two species intergrade in eastern Canada; intermediate specimens were named C. alpinum var. strigosum Hultén.
Cerastium arcticum differs from C. alpinum, with which it often grows, in its straight, somewhat fuscous hairs; calyx which is round at the base; long, narrowly lanceolate sepals; large, straight, broad capsules; and broad, obtuse cauline leaves. Like C. alpinum, it usually has large flowers with the petals much longer than the sepals.
Many infraspecific taxa have been named in Cerastium alpinum but in North America it is much less variable than elsewhere. Two forms can be recognized at either the varietal or subspecific level.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species ca. 100 (27 in the flora).
Two names that appear in many North American treatments, Cerastium viscosum Linnaeus and C. vulgatum Linnaeus, have been proposed for rejection (N. J. Turland and M. Wyse Jackson 1997) because they have been a long-standing source of confusion. American authors have frequently applied C. viscosum to C. glomeratum Thuillier but most of the possible lectotypes are referable to C. fontanum. Similarly C. vulgatum has been used for C. fontanum Baumgarten. However the possible lectotypes of C. vulgatum are mixed and most are referable to C. arvense, C. fontanum, and C. glomeratum.
I have not attempted to present an infrageneric classification for Cerastium. Several species groupings can be recognized based on capsule structure. Examples include species with the capsule teeth revolute (coiled outwards like a watch spring), e.g., C. maximum and C. texanum, whereas in most of our species the teeth are erect with their margins outwardly rolled (convolute). Also C. cerastoides is anomalous in having three styles, a straight ovoid-conic capsule, and deeply bilobed petals—characters that have led some authors to place it in the genus Stellaria. Accepting the most recent infrageneric classification (B. K. Schischkin 1936), even with subsequent modifications, does not appear to be warranted. Additional study is needed to determine relevant species relationships within the genus.
While the base chromosome number for Cerastium is often cited as x = 9, only a single count of 2n = 18 is known; see C. Favarger and M. Krähenbühl (1996) for a discussion of the diverse cytological conditions found in Cerastium.
Excluded species:
Cerastium clawsonii Correll, described from Texas, is a synonym of Linum hudsonioides Planchet (R. L. Hartman 1979).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaf blades on flowering shoots narrowly elliptic or lance-elliptic to oblanceolate, apex ± acute, pubescence evenly distributed, not very dense; inflorescences usually (1-)2-4-flowered | subsp. alpinum |
1. Leaf blades on flowering shoots lance-elliptic to ovate or obovate, apex obtuse, pubescence a tuft of longer, silvery, ± tangled hairs at apex; inflorescences usually 1-flowered | subsp. lanatum |
1. Capsules straight, teeth becoming outwardly coiled | → 2 |
1. Capsules usually curved (rarely straight), teeth erect or sometimes spreading, never coiled, margins convolute | → 3 |
2. Petals less than 10 mm | C. texanum |
2. Petals (15-)18-25 mm | C. maximum |
3. Plants annual, with all shoots producing flowers | → 4 |
3. Plants perennial, often with nonflowering shoots | → 15 |
4. Styles 3-4(-5); capsules with 6, 8 (10) teeth | → 5 |
4. Styles 5; capsules with 10 teeth | → 6 |
5. Styles 4(-5); stamens 4(-5); capsules 1-1.5 times as long as sepals; cauline leaves ovate to oblong-ovate | C. diffusum |
5. Styles 3(-4); stamens 10; capsules ca. 2 times as long as sepals; cauline leaves linear to linear-lanceolate | C. dubium |
6. Bracts, at least distalmost, with scarious margins | → 7 |
6. Bracts all completely herbaceous | → 9 |
7. Stamens 10 | C. fontanum |
7. Stamens 5 | → 8 |
8. Sepals and distal bracts with broad, scarious margins; petal veins not branched | C. semidecandrum |
8. Sepals and distal bracts with very narrow, scarious margins; petal veins branched | C. pumilum |
9. Sepals with long hairs exceeding sepal tips | → 10 |
9. Sepals with hairs shorter than sepal tips | → 11 |
10. Pedicels shorter than capsules; cauline leaf blades broadly ovate or elliptic-ovate | C. glomeratum |
10. Pedicels longer than capsules; cauline leaf blades lanceolate or elliptic | C. brachypetalum |
11. Flowers racemosely arranged singly in axils of foliaceous bracts along length of stem | C. axillare |
11. Flowers in terminal dichotomous cymes or clusters | → 12 |
12. Capsules narrowly conic, straight; stamens 5; pedicels shorter than sepals | C. dichotomum |
12. Capsules cylindric, curved; stamens 10; pedicels shorter than, equaling, or usually longer than sepals | → 13 |
13. Pedicels equaling or shorter than capsules, often becoming deflexed proximally | C. brachypodum |
13. Pedicels longer than capsules, sharply deflexed distally | → 14 |
14. Sepals ovate-lanceolate, apex broadly acute to obtuse, inner with broad, scarious margins (ca. as wide as herbaceous center); mid-stem leaf blades lanceolate to narrowly elliptic, 10-60 × 3-15 mm; capsules (9-)10-12(-13) mm | C. nutans |
14. Sepals narrowly lanceolate, apex sharply acute to acuminate, inner with narrow, scarious margins (narrower than herbaceous center); mid-stem leaf blades linear-lanceolate, 20-70 × 1.5-6 mm; capsules (5-)7-10(-11) mm | C. fastigiatum |
15. Styles 3 (rarely to 6); capsules straight, ovoid-conic, oblong after dehiscence, teeth 6 (rarely to 12) | C. cerastoides |
15. Styles 5; capsules usually curved, rarely straight, cylindric (rarely broadly conic), teeth 10 | → 16 |
16. Small tufts of leaves in axils of mid and proximal stem leaves | → 17 |
16. Small tufts of leaves usually absent from axils of mid and proximal stem leaves (normal leafy shoots may be present) | → 20 |
17. Petals 7.5-9 mm; sepals 3.5-6(-7) mm; flowering stems 5-20(-30) cm; anthers 0.8-0.9 mm | C. arvense |
17. Petals 10-15 mm; sepals 5-9 mm; flowering stems 15-45 cm; anthers 0.9-1.2 mm | → 18 |
18. Plants taprooted, tufted, with or without short, nonflowering, leafy shoots; pubescence on proximal stem spreading; e North America | C. velutinum |
18. Plants with long-creeping rhizomes; pubescence on proximal stems deflexed | → 19 |
19. Capsules 2.5-4 mm wide; sepals 5-7 mm; seeds 0.6-1.2 mm; introduced lawn weed | C. arvense |
19. Capsules 4-5 mm wide; sepals 6-9 mm; seeds 1-1.5 mm; Pacific coastal region | C. viride |
20. Leaf surfaces obscured by dense white tomentum | C. tomentosum |
20. Leaf surfaces clearly visible through pubescence or leaf blades glabrous | → 21 |
21. Long flexuous hairs present on stems and/or leaf blades | C. alpinum |
21. Long flexuous hairs absent, pubescence of straight or deflexed, short or long hairs | → 22 |
22. Gland-tipped hairs absent, pubescence eglandular throughout | → 23 |
22. Gland-tipped hairs present at least in inflorescences | → 24 |
23. Inflorescences with 3+ flowers; stems 10-45 cm; leaves not marcescent; ubiquitous weed | C. fontanum |
23. Inflorescences with 1(-3) flowers; stems 3-7 cm; proximal leaves marcescent; w arctic native | C. aleuticum |
24. Testa of seeds inflated, loose (rubs off when rolled between finger and thumb); Newfoundland | C. terrae-novae |
24. Testa of seeds not inflated, closely and firmly enclosing seed; North America, rarely in Newfoundland | → 25 |
25. Plants pulvinate; stems 1-10 cm | → 26 |
25. Plants rhizomatous, mat-forming or tufted, not pulvinate; stems 5-50 cm | → 27 |
26. Plants rarely flowering; leaf blades subglabrous or with few colorless cilia | C. regelii |
26. Plants normally flowering; leaf blades densely hispid with long, fuscous hairs | C. bialynickii |
27. Petals ± equaling sepals | → 28 |
27. Petals 1.5-2 times as long as sepals | → 29 |
28. Proximal bracts foliaceous | C. beeringianum |
28. Proximal bracts herbaceous, lanceolate, reduced | C. fontanum |
29. Sepals 6-11 mm, narrowly lanceolate-triangular, apex acute or acuminate, scarious margins narrow | → 30 |
29. Sepals 3-7 mm, lanceolate to broadly elliptic, apex obtuse to ± acute, scarious margins broad | → 31 |
30. Apices of mid and distal stem leaf blades acute; pubescence on stem and leaf blades long, dense, yellowish; inflorescences 2-10-flowered; w arctic | C. fischerianum |
30. Apices of mid and distal stem leaf blades usually round and obtuse; pubescence colorless to somewhat fuscous; inflorescences 1-3-flowered; e arctic | C. arcticum |
31. Sepals with ± acute apex; leaf blades not succulent, pubescent, those on flowering shoots with ± acute apex; petals usually equaling, rarely to 2 times as long as sepals; plants taprooted, forming clumps, rarely rhizomatous | C. beeringianum |
31. Sepals with obtuse apex; leaf blades succulent, subglabrous to ciliate with long, colorless hairs, rotund, obovate, broadly elliptic, or broadly lanceolate, apex obtuse; petals 1.5-2 times as long as sepals; plants strongly rhizomatous with nonflowering, creeping shoots 6-30 cm | C. regelii |
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