Platanthera nivea
Platanthera limosa
snowy orchid
Thurber's bog orchid
1–3, ascending to spreading, abruptly or gradually reduced to bracts distally, often fugaceous and withered at anthesis;
blade linear to linear-lanceolate, 3–31 × 0.3–2 cm.
few to several, spreading-ascending on base of stem, gradually reduced to bracts upwards;
blade lanceolate, 9–28 × 1.2–3.5 cm.
dense.
dense to lax.
not resupinate, showy, white;
lateral sepals spreading;
petals linear-oblong to oblong or elliptic, falcate, basally somewhat dilated, margins entire;
lip reflexed ± at middle, linear-elliptic to linear-oblong, without basal thickening, 3–8 × 1–3 mm, margins entire;
spur slenderly cylindric, 10–18 mm;
rostellum lobes directed downward, very short, obscure, rounded;
pollinaria straight, pollinia remaining enclosed in anther sacs;
viscidia oblong to linear-oblong;
ovary slender, 4–12 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.
Platanthera nivea
Platanthera limosa
The column of Platanthera nivea is similar to that of P. clavellata and P. integra and unlike that of other Platanthera species. The columns of these three species bear two pairs of appendages. In P. nivea, on either side of the column and flanking the anther sacs, a cushionlike flap simulates a pollinium; below these structures, elongated slender processes parallel the basal margins of the lip, similar to the situation in Habenaria. Together with its non-resupinate flower and perhaps elongate-spheroidal tuberoids, these characteristics suggest that this species should not be included in Platanthera.
(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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