Ivesia muirii
Ivesia sericoleuca
granite mousetail, Muir's ivesia
Plumas ivesia, Plumas mousetail
usually ± erect, sometimes nearly prostrate, 0.5–1.5(–2) dm.
decumbent to ascending, 1.5–4.5 dm.
very tightly cylindric (mousetail-like, with individual leaflets scarcely distinguishable), 2–5(–10) cm; sheathing base densely strigose abaxially;
petiole 0.2–0.8(–1) cm, hairs 0.5–1.5 mm;
leaflets 25–40 per side, 0.4–1 mm, densely sericeous, glands obscured, lobes 2–5, obovate or oval to orbiculate, apex not setose.
10–20(–30) cm; sheathing base densely strigose abaxially;
stipules absent;
petiole 2–6(–10) cm, hairs abundant, usually spreading, 1–4 mm;
leaflets 20–35 per side, loosely overlapping, 3–15 mm, lobes 0–4, oblanceolate to elliptic, hairs abundant, spreading to ascending, (0.5–)1–3(–4) mm.
(0–)1–2, paired if 2.
3–8(–10).
10–30-flowered, 1–2(–3.5) cm diam.;
glomerules usually 1.
20–120-flowered, (2–)4–14 cm diam., flowers mostly arranged in several to many tight glomerules of 5–10 flowers.
0.3–2(–3.5) mm.
1–3(–12) mm.
5–6 mm diam.;
epicalyx bractlets oblong to obovate, 0.5–1 mm;
hypanthium shallowly cupulate, 0.5–1(–1.5) × 1.5–2.5 mm;
sepals (1–)1.5–2.5 mm, acute;
petals yellow, linear to oblanceolate or narrowly oblong, 1–2 mm;
stamens 5, filaments 0.3–0.6 mm, anthers yellow, 0.4–0.6 mm;
carpels 1–4, styles 0.7–1.2 mm.
10–15 mm diam.;
epicalyx bractlets narrowly lanceolate to narrowly elliptic, (1.5–)2–2.5(–3) mm;
hypanthium campanulate to shallowly turbinate, 1.5–3 × 2.5–4.5(–5) mm, often nearly as deep as wide;
sepals sometimes purple-suffused, 3–5.5 mm, acute to acuminate;
petals white, broadly spatulate to broadly obovate or obcordate, 4–7 mm;
stamens 20, filaments filiform, 1.5–3 mm, anthers white to cream, 0.5–0.7 mm;
carpels 2–7, styles 2.5–4 mm.
grayish brown, mottled with red, 1.6–2 mm.
brown, 2–3 mm.
= 28.
Ivesia muirii
Ivesia sericoleuca
Ivesia muirii is known from alpine areas in the Sierra Nevada. It is one of the more distinctive species of the genus, in its silvery mousetail-like leaves and usually tightly capitate inflorescences. Putative hybrids are known with I. lycopodioides (D. D. Keck 1938) and I. pygmaea (Center Basin area of Tulare County).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Of conservation concern.
Ivesia sericoleuca is known from valleys and flats in the northern Sierra Nevada. Many historic collections were identified and distributed as I. unguiculata, and circumscriptions prior to 1962 include I. aperta (hence reports from Nevada).
Hairs are usually dense in plants of Ivesia sericoleuca, such that the leaves, and occasionally the stems and branches, are silvery gray, especially in Sierra Valley and the Feather River drainage. Plants in the Truckee River drainage tend to be less hairy with redder stems, less glomerate inflorescences, shallower hypanthia, and more conspicuous glandularity.
As mentioned by J. T. Howell (1962), the chromosome count given for Ivesia sericoleuca by P. A. Munz (1959) most likely was based on a collection of I. aperta var. aperta. The chromosome count given here is instead based on Kruckeberg 3665, originally distributed as I. pickeringii.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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