Glyceria alnasteretum
Glyceria ×occidentalis
Aleutian glyceria
northwestern manna grass, western manna grass
60-90 cm tall, 2.5-4 mm thick, erect.
60-160 cm tall, 2.5-5 mm thick, erect or decumbent and rooting from the lower nodes.
smooth, not keeled;
ligules 2-3 mm, rounded to truncate;
blades 5-20 cm long, 3-7 mm wide, abaxial surfaces smooth, adaxial surfaces scabrous, apices acute.
smooth to scabridulous, keeled, sometimes weakly so;
ligules 7-12 mm;
blades 20-30 cm long, (2.5)4-12 mm wide, adaxial surfaces scabridulous, occasionally papillose.
15-22 cm long, 12-16 cm wide, open, pyramidal, erect to nodding;
branches 8-10 cm, lower branches widely divergent to drooping.
20-50 cm long, 2-15 cm wide, usually narrow, open at anthesis;
branches 4.5-18 cm, somewhat lax, usually ascending, strongly divergent at anthesis, with 2-8 spikelets, pedicels 1.5-8 mm.
7-9 mm long, 3-4.5 mm wide, with 5-8 florets.
13-23 mm long, 1.5-3.5 mm wide, cylindrical and terete, except at anthesis when slightly laterally compressed, rectangular in side view, with 6-13 florets.
unequal, lanceolate, acute;
lower glumes 2-3.5 mm;
upper glumes 2.5-3.5 mm, longer than wide;
lemmas 3-5.5 mm, 7-veined, obtuse to acute;
paleas shorter than or subequal to the lemmas, keels not winged, apices not strongly incurved, emarginate between the keels;
anthers 3, 0.7-1.2 mm.
acute to obtuse;
lower glumes 1.1-2.8 mm;
upper glumes 2.9-3.7 mm, about twice as long as the lower glumes;
rachilla internodes 1-2.8 mm;
lemmas 4.5-5.9 mm, scabridulous, midveins extending to within 0.1 mm of the apical margins, apices acute, usually slightly lobed or irregularly crenate;
paleas usually shorter than or equaling the lemmas, sometimes slightly longer, keels winged, apices shallowly notched to slightly bifid, teeth to 0.2 mm, parallel;
anthers 2, 0.6-1.6 mm.
not seen.
= 20.
= 40.
Glyceria alnasteretum
Glyceria ×occidentalis
Glyceria alnasteretum is included in this treatment with some hesitation, based on van Schaack 724 (W'l'LJ 152646) and van Schaack 887 (MO 1710727), both collected at Signal Point, Attu Island, Alaska in 1945. The above description is based on Komarov (1963) and Koyama (1987), modified to reflect the wider panicles and longer glumes and lemmas of the van Schaack specimens. The difference in habitat is troubling. The van Schaack specimens were found "in a beachside meadow" and "near beach." Koyama describes the habitat of G. alnasteretum as "wet meadows and marshes at high altitudes as well as subarctic zone" (p. 114). Nevertheless, the van Schaack specimens fit the description of G. alnasteretum better than any other taxon in this treatment. Clearly, further investigation is called for; it should include plants from both sides of the Bering Strait.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Glyceria ×occidentalis has hitherto been considered an uncommon native species that grows along lakes, ponds, and streams, and in marshy areas of western North America. It differs from other species in the region primarily in its longer lemmas and anthers. Studies of chloroplast DNA in western North American species of Glyceria demonstrated that, contrary to C.L. Hitchcock's (1969) conclusion, G. fluitans is present in western North America, and that all specimens being identified as G. ×occidentalis had cpDNA resembling that of G. leptostachya or G. fluitans; there was no distinctive G. ×occidentalis cpDNA (Whipple et al. [in press]). This strongly suggests that G. ×occidentalis is a series of reciprocal hybids, and probably backcrosses, between G. fluitans and G. leptostachya. As the key indicates, G. ×occidentalis is intermediate between its two putative parents. The cpDNA study also confirmed that G. declinata is distinct from G. ×occidentalis (see discussion under that species).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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