Geum rossii
Geum laciniatum
alpine avens, Ross' avens, slender stem avens
benoîte lacinicée, floodplain avens, hairy herb-bennet, rough avens
4–28 cm, glabrous or downy, hairs to 1 mm, sometimes septate-glandular.
30–100 cm, hirsute, some hairs 2–2.5 mm.
basal 3–13 cm, blade pinnate to interruptedly pinnate, major leaflets 13–26, alternating with 0–14 minor ones, terminal leaflet slightly larger than major laterals;
cauline 0.7–2 cm, stipules adnate to leaf, indistinguishable from pair of lobes, blade bractlike, not resembling basal, alternate, simple, pinnatifid to 3-fid.
basal 15–32 cm, blade simple, lyrate-pinnate, or pinnate, major leaflets 1–7, alternating with 0–10 minor leaflets, terminal leaflet slightly to much larger than major laterals;
cauline 3.5–18 cm, stipules ± free, 4–14 × 7–17 mm, blade pinnate, 3-foliolate, or simple and unlobed.
1–3(–4)-flowered.
2–9-flowered.
woolly, sometimes glandular.
densely puberulent, hirsute, eglandular.
erect;
epicalyx bractlets 1.5–7 mm;
hypanthium green, slightly purple-tinged to strongly purple;
sepals erect to erect-spreading, 3–10 mm;
petals spreading, yellow, obovate to nearly orbiculate, 5–12(–17) mm, longer than sepals, apex broadly rounded to irregularly emarginate.
erect;
epicalyx bractlets 1–2 mm;
hypanthium green;
sepals spreading but soon reflexed, 3–10 mm;
petals spreading, white, oblong to elliptic, 2–5 mm, shorter than sepals, apex obtuse to rounded.
sessile, glabrous.
sessile, glabrous except for ring of bristles at base and tuft at apex.
wholly persistent, not geniculate-jointed, 2–5(–10) mm, apex not hooked, glabrous throughout or pilose only at base.
geniculate-jointed, proximal segment persistent, 2.5–5 mm, apex hooked, glabrous, sometimes 1–2 eglandular bristles at base, distal segment deciduous, 1–2 mm, short hairs on basal 1/2.
= 56.
= 42.
Geum rossii
Geum laciniatum
The variability accommodated here in Geum rossii was distributed by earlier monographers such as P. A. Rydberg (1913b) and F. Bolle (1933) among a half dozen species. W. Gajewski (1957) reduced them to two species, G. rossii and G. turbinatum; most recent taxonomists have recognized the two taxa as subspecies or varieties of a single species. The large geographic discontinuity between the Rocky Mountain and arctic ranges makes it easy for those wishing to follow this tradition. No one morphologic character or combination of characters neatly separates the arctic plants from those of the Rockies.
Where their ranges overlap in Alaska, Geum rossii hybridizes with G. calthifolium to form sterile plants known as G. ×macranthum (Kearney ex Rydberg) B. Boivin; see discussion under 4. G. schofieldii.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
B. L. Robinson and M. L. Fernald (1908) and J. K. Small (1933) misapplied the name Geum virginianum to this species. As a consequence, older specimens of G. laciniatum are often labeled (and filed in herbaria) as G. virginianum.
Geum laciniatum is unique among members of the genus in having some of the heads of achenes pop off the stem and disperse as a unit. The heads disarticulate where the torus joins the hypanthium, leaving the hypanthium inverted at the tip of the stem.
Fernald described var. trichocarpum based on the presence of bristles on the summits of the achenes. Although this morphology occurs to the near exclusion of the glabrous one in the western part of the species range, it also occurs as far east as the Carolinas, Maine, New Jersey, and Virginia. The glabrous condition has a smaller range, and it is the prominent one in Nova Scotia, Kentucky, Maine, and Ohio. The two are well mixed in Quebec, New York, and Pennsylvania. Although they are easily distinguished (hairs absent versus present), they seem to have little phytogeographic significance, and presence of achene hairs is not correlated with any other characteristics. It appears to be a trivial variation.
Geum laciniatum hybridizes with G. urbanum (= G. ×macneillii J.-P. Bernard & R. Gauthier); see discussion under 15. G. urbanum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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