Saxifraga paniculata
Saxifraga debilis
saxifrage paniculée, White Mountain saxifrage
pygmy saxifrage, weak saxifrage
basal and cauline;
petiole absent;
blade oblong to obovate, unlobed, [5–]8–35[–50] mm, leathery-fleshy, margins finely serrate (teeth whitish), proximally ciliate, with lime-secreting hydathode (secretions obvious), apex obtuse to ± acute, surfaces glabrous.
basal and cauline, (3–5, proximal similar to basal);
petiole ± flattened, 5–70 mm;
blade round or reniform, (3–)5–7-lobed (lobes obtuse), (3–)4.5–6.7(–10.3) mm, slightly fleshy, margins entire, eciliate, surfaces glabrous.
2–20-flowered, narrow, distally branched thyrses or cymes, sometimes solitary flowers, 6–40 cm, purple-tipped stipitate-glandular;
bracts sessile.
2–3(–5)-flowered, capitate cymes, sometimes solitary flowers, (flowers subsessile), (3–)6.7–9(–19.4) cm, tangled, nonglandular-hairy;
bracts petiolate.
sepals erect, (often reddish), oblong to ovate, margins eciliate, surfaces hairy;
petals white to cream or pink, sometimes orange- or purple-spotted, elliptic to oblong or obovate, 3–6 mm, longer than sepals;
ovary 1/2+ inferior.
(hypanthium V-shaped in longisection, glabrous or sparsely short stipitate-glandular);
sepals erect, oblong to ovate, (0.7–1 mm wide), margins eciliate, surfaces abaxially glabrous;
petals white to pale purple, not spotted, oblong, (1.7–)3–4.4(–6.2) mm, ± equaling sepals;
ovary 1/2 inferior.
= 28.
= 26.
Saxifraga paniculata
Saxifraga debilis
C. Reisch (2008) studied the phylogeography of Saxifraga paniculata. North American populations originated postglacially from refugia south of the ice. Reisch suggested that North American populations may belong to subsp. laestadii (Neuman) T. Karlsson, found also in Iceland and northern Norway. The Manitoba report originates from Clearwater Lake (R. Humphrey s.n., 13 Sept. 1993, WIN 62868), where shaded, cool, calcareous cliffs provide suitable habitats that also host other eastern disjuncts (B. A. Ford, pers. comm.).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Saxifraga debilis is known only from the central and southern Rocky Mountains, where it is often called S. rivularis (a species not present in the area). Its V-shaped (in longisection), glabrous or sparsely short stipitate-glandular hypanthia, and larger, more-lobed leaves (similar to S. bracteata in this) distinguish it from S. hyperborea, which is sometimes sympatric (M. H. Jørgensen et al. 2006).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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