Ivesia pickeringii
Ivesia sericoleuca
Pickering's ivesia, silky mousetail
Plumas ivesia, Plumas mousetail
ascending to erect, 3–5 dm.
decumbent to ascending, 1.5–4.5 dm.
8–20 cm; sheathing base ± strigose abaxially;
stipules linear to narrowly lanceolate, 3–5 mm;
petiole 1–3.5 cm, hairs abundant, ascending to spreading, 1–2 mm;
leaflets 35–50 per side, loosely overlapping, 2–6 mm, lobes 3–5, oblanceolate to obovate or oval, hairs abundant, ± ascending, 1–2(–3) mm.
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.
5–10.
3–8(–10).
10–100-flowered, (1.5–)5–15 cm diam., flowers usually arranged individually, sometimes more congested.
20–120-flowered, (2–)4–14 cm diam., flowers mostly arranged in several to many tight glomerules of 5–10 flowers.
(1–)2–10 mm.
1–3(–12) mm.
8–13 mm diam.;
epicalyx bractlets linear-lanceolate to lanceolate, (1.8–)2–2.5 mm;
hypanthium cupulate to turbinate, 1.5–3 × 2.5–4 mm, often nearly as deep as wide;
sepals often purple-suffused or -mottled, (2.5–)3–5 mm, acuminate;
petals white, becoming pink-tinged with age, oblanceolate to narrowly spatulate, (2.8–)3–5(–6) mm;
stamens 20, filaments filiform, 1.5–2.3 mm, anthers white to cream, 0.3–0.6 mm;
carpels 2–4, styles 2.5–3.5 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.
dark brown, 2.5–3 mm.
brown, 2–3 mm.
= 28.
Ivesia pickeringii
Ivesia sericoleuca
Of conservation concern.
Ivesia pickeringii is known from Siskiyou and Trinity counties. Some early treatments (for example, P. A. Rydberg 1898, 1908–1918; W. L. Jepson [1923–1925], 1909–1943, vol. 2) conflated this species with I. aperta, hence reports of I. pickeringii in the Sierra Nevada. Historic collections from Edgewood, at the headwaters of the Shasta River in Siskiyou County, have inflorescences more glomerulate than elsewhere in the species range.
The chromosome count of 2n = 28 (P. A. Munz 1959) needs confirmation. If based on Kruckeberg 3665, which was distributed as a voucher for that count, the determination of this collection has been changed to Ivesia sericoleuca.
(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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