Platanthera nivea
Platanthera praeclara
snowy orchid
Great Plains white fringe orchid, western prairie fringe 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.
several to many, ascending, scattered along stem, imperceptibly reduced to bracts distally;
blade lanceolate to ovate-lanceolate, to 26 × 5 cm.
dense.
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, showy, creamy white;
lateral sepals somewhat porrect;
petals flabellate, truncate, sometimes emarginate, apically lacerate;
lip descending, deeply 3-lobed, without basal thickening, 17–32 × 20–39 mm, distal margins of lobes deeply incised and fringed, lateral lobes flabellate, sometimes broadly and overlapping middle lobe, middle lobe flabellate, sometimes very broadly, emarginate;
spur slenderly clavate, 36–55 mm;
rostellum lobes directed strongly forward, wide-spreading, angular;
pollinaria geniculate;
pollinia directed forward (column appearing hooded), remaining enclosed in anther sacs;
viscidia orbiculate;
ovary slender, mostly 20–30 mm.
= 42.
Platanthera nivea
Platanthera praeclara
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.)
Of conservation concern.
In Platanthera praeclara the wide-spreading rostellum lobes separate the viscidia by 6–7.5 mm, whereas in P. leucophaea the short rostellum lobes are more nearly parallel, and the viscidia are separated only by about 1–3.5 mm. These differences are immediately obvious on living material, but the measurements are nearly always impossible in herbarium specimens.
In Wyoming Platanthera praeclara is known from a single, much higher station outside the usual range.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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