Platanthera macrophylla
Platanthera obtusata
greater roundleaf orchid, large round-leaf orchid, large-leaf bog-orchid
blunt-leaf bog-orchid, blunt-leaf rein-orchid, blunt-leafed rein orchid, bluntleaf orchid, northern small bog orchid, one-leaf rein-orchid, small northern bog-orchid
2, in subequal basal pair lying on ground;
bracts (very rarely, 0–)1–6, scattered along stem;
blade broadly elliptic, orbiculate, or oblate, 7–24 × 5–19 cm.
1(–2, rarely), spreading-ascending on base of stem;
bracts 0(–1, rarely);
blade linear-oblanceolate, elliptic, or broadly obovate, 3.5–15 × 0.8–5 cm.
lax.
lax.
resupinate, rather showy;
calyx mostly greenish white;
corolla mostly white;
lateral sepals reflexed to somewhat spreading;
petals lanceolate-falcate, margins entire;
lip descending to somewhat reflexed, linear-oblong to linear-lanceolate, without basal thickening, 10–23 × 1–2.5 mm, margins entire;
spur slenderly clavate, 28–46 mm;
rostellum lobes directed strongly forward, wide-spreading, angular;
pollinaria nearly straight, (4.6–)4.7–6.8 mm;
pollinia remaining enclosed in anther sacs;
viscidia orbiculate;
ovary slender to rather stout, mostly 16–29 mm.
resupinate, not showy, greenish white to yellowish green;
corolla commonly whiter than calyx;
lateral sepals reflexed;
petals rhombic, lanceolate-falcate, margins entire;
lip descending, linear, narrowly lance-rhombic, or linear-hastate, with median basal thickening, unlobed, 2.5–8(–10) × less than 1–2 mm, margins entire;
spur slenderly conic, 3–8(–10) mm;
rostellum lobes directed forward, wide-spreading, rounded-angular;
pollinaria straight;
pollinia remaining enclosed in anther sacs;
viscidia orbiculate;
ovary rather slender to stout, mostly 3–10 mm.
= 42, 63 (American, as Habenaria obtusata), 126 (Eurasian, as Habenaria obtusata).
Platanthera macrophylla
Platanthera obtusata
The rare Eurasian Platanthera obtusata subsp. oligantha (Turczaninow) Hultén differs from the North American subsp. obtusata in its smaller dimensions and rhombic-lanceolate lip. It is also said to be densely few-flowered, although some Siberian material is comparable to American plants. Supposedly intermediate plants are reported from Alaska, and much material from that area is reduced in stature and with smaller flowers than typical of American plants. In most cases, however, lips are relatively slender, and the plants seem merely to be stunted by their environment. One or two collections from the Alaskan Peninsula and Aleutians, however, seem entirely referable to subsp. oligantha with dense, few-flowered inflorescences of very small flowers with rhombic-lanceolate lips and shorter curved spurs. Eurasian plants are reported to be hexaploid or perhaps sometimes triploid, and if the apparent ploidy differences delimit the taxa, then it should be possible to unequivocally identify Alaskan plants.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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