Platanthera orbiculata
Platanthera integra
large round-leaf orchid, large round-leaf rein orchid, lesser roundleaf orchid, round-leaf bog-orchid, round-leaf orchid
yellow fringeless orchid
2, in subequal basal pair lying on ground;
bracts (very rarely, 0–)1–6, scattered along stem;
blade broadly elliptic to orbiculate or oblate, 5–21 × 3–22 cm.
1–3, ascending to spreading, rather abruptly or gradually reduced to bracts distally;
blade lance-oblong to linear-lanceolate, 4.5–32 × 1–3 cm.
lax to dense.
dense.
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, 7–17 × 1–2.5 mm, margins entire;
spur slenderly clavate, 14–27 mm;
rostellum lobes directed strongly forward, wide-spreading, angular;
pollinaria nearly straight, 3–4.5(–4.8, very rarely) mm;
pollinia remaining enclosed in anther sacs;
viscidia orbiculate;
ovary slender to rather stout, mostly 10–26 mm.
resupinate, showy, pale yellow-orange to pale orange;
dorsal sepal entire or rarely apically dentate;
lateral sepals spreading;
petals elliptic to linear-oblong, margins entire;
lip descending, ovate-elliptic to obovate or oblong, 3–5 × 1.5–4 mm, margins eroded to lacerate or rarely entire, with basal pair of fleshy ridges on adaxial surface;
spur tapering from broad base to slender tube, 5–10 mm;
rostellum lobes curved downward, short, rounded;
pollinaria essentially straight; large pollinia protruding forward;
viscidia orbiculate to suborbiculate;
ovary slender to somewhat stout, 5–11 mm.
= 42.
Platanthera orbiculata
Platanthera integra
The key will permit determination of most specimens of Platanthera orbiculata and P. macrophylla. More precise discrimination of ambiguous specimens is possible by use of the formula from A. H. Reddoch and J. M. Reddoch (1993): spur length + (2 × pollinarium length), which for P. orbiculata is less than 38 and for P. macrophylla is equal to or greater than 38.
Considerable variation in size and shape of leaves occurs, and although to some extent regional in nature, intergradation is complete; recognition of infraspecific taxa is unwarranted. A few collections from isolated areas on the Pacific Coast of Canada are noteworthy, however. Those are small, few-flowered plants with rather narrow leaves borne alternately or suboppositely toward the base of the stem, as in some Asiatic species. They are in some respects very similar to Platanthera freynii Kränzlin, an Asiatic species distinguished primarily by its abruptly narrowed petals, in contrast to the generally broader, but variable, petals in North American plants. These western plants warrant further study to establish their identity and to elucidate relationships between North American and Asiatic species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
As in Platanthera clavellata and P. nivea, the column of P. integra bears two pairs of lateral processes. In P. integra, the distal structures are essentially sessile and cushionlike, as in P. nivea, but the proximal are short, stout, clublike, and bear several stout horns. The tuberoids of P. integra are abruptly swollen into oblong-cylinders, somewhat like those of P. nivea. These three species evidently form a group apart from Platanthera. See note under 30. P. nivea.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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PNW Herbaria, Turner Photog. 
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