Platanthera obtusata
Platanthera limosa
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
Thurber's bog orchid
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.
few to several, spreading-ascending on base of stem, gradually reduced to bracts upwards;
blade lanceolate, 9–28 × 1.2–3.5 cm.
lax.
dense to lax.
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.
resupinate, inconspicuous, green;
lateral sepals reflexed to spreading;
petals lanceolate-, ovate-oblong-, or ovate-falcate, margins entire;
lip descending to reflexed, linear-oblong, linear-elliptic, or rhombic-ovate, usually with inconspicuous to scarcely discernable (possibly sometimes absent) median basal thickening, 2.5–8.5 × less than 1–3.5 mm, margins entire;
spur filiform, tapering toward apex, very rarely filiform-conic from slightly stout base, 8–25 mm;
rostellum lobes mostly parallel, closely spaced, directed downward, very small, rounded, obscure;
pollinaria straight;
pollinia remaining enclosed in anther sacs;
viscidia evidently elliptic-oblong;
ovary rather slender to stout, mostly 4.5–11 mm.
= 42, 63 (American, as Habenaria obtusata), 126 (Eurasian, as Habenaria obtusata).
Platanthera obtusata
Platanthera limosa
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.)
Platanthera limosa is traditionally distinguished from other slender-spurred plants and from P. sparsiflora by the presence on the lip of a median thickening that culminates in a small basal process. Although diagnostic when present, this feature is often obscure, especially in live material, and seems to be lacking in some plants. Platanthera limosa is most consistently separated from other green-flowered species by the combination of very small, narrow column and slender spur much longer than the lip. These features are in contrast to the very large, broad columns of P. sparsiflora and P. zothecina and much shorter spurs of the P. hyperborea complex. The lips of most plants are elliptic to elliptic-oblong, unlike any other species except the Aleutian P. tipuloides, and such plants are readily determined by lip shape and spur characters. Within populations plants may vary greatly in flower size, spur shape and length, and the ratio of spur to lip length. Individual plants may vary markedly in size of the flowers and density of the inflorescence in different years. That situation warrants additional study, as it may obscure the presence of other taxa.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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