Salix rotundifolia
Salix cinerea
least willow, round-leaf willow
gray willow, large gray or gray willow, large gray willow
erect;
branches yellow-green, yellow-brown, or gray-brown, glabrous;
branchlets yellow-brown or red-brown, glabrous;
branches and branchlets sometimes weakly glaucous.
(marcescent but not skeletonized), stipules usually absent or rudimentary, rarely present on late ones;
petiole (convex, or shallowly to deeply grooved, flat), 0.4–4.6(–5.5) mm, (glabrous adaxially);
largest medial blade (2 pairs of secondary veins arising at or close to base, arcing toward apex) broadly elliptic, subcircular, or circular, 1.9–16.3 × 3–10.5 mm, 0.84–1.17(–2.53) times as long as wide, base rounded or convex, margins flat, entire, ciliate, apex retuse, rounded, convex, or acute, abaxial surface glabrous, adaxial highly glossy, glabrous;
proximal blade margins entire;
juvenile blade glabrous or puberulent.
stipules rudimentary or foliaceous on early ones, foliaceous on late ones, apex acute or rounded;
petiole convex to flat adaxially, 4–15 mm, tomentose adaxially;
largest medial blade elliptic, broadly elliptic, oblanceolate, or obovate, 65–105 × 22–52 mm, 2–3 times as long as wide, base convex or cuneate, margins slightly revolute, entire, crenate, or sinuate, (glands submarginal), apex acuminate or convex, abaxial surface glaucous, tomentose, hairs erect or spreading, curly, adaxial dull or slightly glossy, pubescent or tomentose;
proximal blade margins entire;
juvenile blade yellowish green, sparsely to densely tomentose abaxially, hairs white.
abaxial nectary 0.5–1 mm, adaxial nectary narrowly oblong or oblong, 0.8–1.4 mm, nectaries distinct;
filaments distinct or connate less than 1/2 their lengths, glabrous;
anthers ellipsoid or globose, 0.4–0.6 mm.
adaxial nectary oblong or ovate, 0.5–1 mm;
filaments distinct, glabrous or hairy basally;
anthers yellow or purple turning yellow, ellipsoid or shortly cylindrical, 0.7–1 mm.
abaxial nectary present or absent, adaxial nectary usually narrowly oblong or oblong, sometimes flask-shaped, 0.8–2 mm, longer than stipe;
stipe 0.4–0.8 mm;
ovary pyriform, glabrous or puberulent, (hairs in patches, especially on beak), beak slightly bulged below styles;
ovules 7–17 per ovary;
styles connate or slightly distinct distally, 0.5–1 mm;
stigmas flat, abaxially non-papillate with pointed tip, or slenderly or broadly cylindrical, 0.28–0.6 mm.
adaxial nectary oblong or square, 0.4–1 mm, shorter than stipe;
stipe 1.2–2.7 mm;
ovary pyriform, long-silky, beak slightly bulged below styles;
ovules 12 per ovary;
styles 0.2–0.5 mm;
stigmas slenderly or broadly cylindrical, 0.3–0.6 mm.
3.8–8.3 mm.
5–5.6 mm.
from subterminal buds; staminate subglobose, stout, or indeterminate, 3.3–18.5 × 2.5–12 mm, flowering branchlet 0.5–9 mm; pistillate moderately densely to loosely flowered (2–15 flowers), stout, subglobose, globose, or indeterminate, 4.5–35 × 2–17 mm, flowering branchlet 0.5–22 mm;
floral bract brown, 1.6–2.8 mm, apex rounded or retuse, entire, abaxially sparsely hairy or ciliate, hairs usually wavy, crinkled or curly, rarely straight.
flowering before leaves emerge; staminate stout or subglobose, 26–39 × 12–26 mm, flowering branchlet 0–5 mm; pistillate densely flowered, stout or subglobose, 27–54(–75 in fruit) × 4–15 mm, flowering branchlet 1–5(–10) mm;
floral bract dark brown, black, or bicolor, 2–3 mm, apex acute or convex, abaxially hairy, hairs straight.
= 76.
Salix rotundifolia
Salix cinerea
Varieties 2 (2 in the flora).
Salix rotundifolia is closely related to S. polaris, from which it can be separated by its glabrous ovaries and fewer-flowered catkins. They also differ somewhat in leaf venation: S. rotundifolia typically having three main veins arising from the leaf base, often only one or two pair of secondary veins, and no or indistinct tertiary veins; S. polaris typically having pinnate venation, multiple secondary veins, and distinct tertiary veins. Salix rotundifolia consists of two varieties, the diploid var. dodgeana and the hexaploid var. rotundifolia. In general, var. dodgeana is a high alpine species in the southern cordillera of Wyoming and Montana, the St. Elias Mountains in Alaska and Yukon, the Mackenzie Mountains, Northwest Territories, and the Richardson Mountains, Yukon Territory. A diploid specimen of S. rotundifolia in the Cherski Mountains, Yakutia, Russia (B. A. Jurtzev and P. G. Zhukova 1982), which fits var. dodgeana in its 2–3-flowered catkins, relatively small leaves (3.5 × 3.9 mm), and small stomata (490 µm2), may represent an ancestral population. Variety rotundifolia usually occurs at lower elevations in Alaska and in easternmost Chukotka and Wrangel Island, Russia, but elevation separation is not distinct. There is a general correlation between stomatal size and ploidal level (W. Buechler, pers. comm.), but relatively large stomata in some diploid specimens of S. rotundifolia indicates a need for further cytological study. For the present, it is best to recognize the two cytotypes as varieties.
Hybrids:
Salix rotundifolia forms natural hybrids with S. arctica, S. phlebophylla, and S. polaris.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The Ohio occurrence of Salix cinerea is based on information from T. Cooperrider (pers. comm.).
Salix cinerea and S. atrocinerea are very closely related. Their occurrence in the flora area, as naturalized introductions, is not well understood, probably because they usually are introduced under the name S. caprea, and that species often is not treated in North American floristic literature (e.g., C. K. Schneider 1921; M. L. Fernald 1950). They probably are introductions of long-standing brought to the New World for their value as ornamentals and bee-plants. Salix atrocinerea was first documented in the southeastern United States (G. W. Argus 1986) after plants with ferruginous hairs and prominently striate wood were found in North Carolina; since that time, it has been found in other states and provinces. In the northeastern states, S. atrocinerea and S. cinerea are thought to be invasive species. The species do reproduce by seed and hundreds of seedlings were observed in a drained reservoir (A. Zinovjev, pers. comm.) and on sandy pond shores (T. Rawinski, pers. comm.), where they are thought to compete with native species.
The presence of long, prominent, striae on the peeled wood of 4–5 year old branches is commonly used in European literature (K. H. Rechinger 1993; A. K. Skvortsov 1999) to separate Salix cinerea and S. atrocinerea from S. caprea etc., in which the wood is smooth or with fewer, shorter striae. In the flora area, long striae also occur in S. bebbiana, S. discolor, and S. humilis, but usually they are not as long as or as prominent in S. cinerea and S. atrocinerea. Some floras (e.g., F. Martini and P. Paiero 1988) use the relative prominence of striae to separate S. cinerea and S. atrocinerea, but their separation remains difficult. The presence of ferruginous hairs on the leaves of S. atrocinerea is the best diagnostic characteristic, but they are not always present or easily observed. For a comparison of these species, see the key to species under subg. Vetrix. For further discussion of morphologies, see Salix ×smithiana Willdenow [p. 132] and 76. S. discolor.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Pistillate catkins: (3-)4-7-15 flowers; largest medial blades 4.5-8-16.3 mm, 0.92-1.23-2.27 times as long as wide; petioles 0.5-2-4.6 (-5.5) mm; floral bracts: hairs usually wavy, some straight, curly, or crinkled, exceeding bract by 0.32-0.71-1.25(-2.4) mm; pistillate flowers: abaxial nectaries present or absent; 2n = 114. | var. rotundifolia |
1. Pistillate catkins: 2-4-9 flowers; largest medial blades 2.9-6.1-7.4 mm, 0.84-1.5-2.2 times as long as wide; petioles 0.4-1.1-2.8 mm; floral bracts: hairs usually wavy, crinkled, or curly, rarely straight, exceeding bract by 0.1-0.37-0.75 mm; pistillate flowers: abaxial nectaries absent; 2n = 38. | var. dodgeana |
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