Platanthera obtusata
Platanthera brevifolia
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
platanthera de hoja corta, short-leaf bog-orchid, shortflower 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, ascending-sheathing, little more than bracts, scarcely reduced distally;
bracts often lacking;
blade ovate to elliptic-ovate, 2.5–6 × 0.7–2 cm.
lax.
lax to rather dense.
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, not showy, green to yellowish green;
lateral sepals reflexed or sometimes spreading;
petals ovate- to lance-falcate, margins entire;
lip descending or reflexed, linear to linear-oblong or linear-lanceolate, 6–10(–14) mm, margins entire, often with series of low parallel ridges on adaxial surface;
spur cylindric or tapering toward apex, 9–20 mm, apex usually rather acute;
rostellum lobes somewhat divergent, directed forward, rounded-subangular, rather prominent;
pollinaria straight;
pollinia remaining enclosed in anther sacs;
viscidia orbiculate to broadly elliptic-oblong;
ovary rather slender to stout, mostly 6–12 mm.
= 42, 63 (American, as Habenaria obtusata), 126 (Eurasian, as Habenaria obtusata).
Platanthera obtusata
Platanthera brevifolia
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.)
The greatly reduced herbage of Platanthera brevifolia is distinctive. Robust plants may lack developed leaves altogether, with merely a few reduced bracts at the base of the stem and an inflorescence comprising nearly the entire height of the plant. A strong mycotrophic mode is suggested by the occurrence in some colonies of truly albino plants without pigmentation.
Platanthera brevifolia largely replaces P. sparsiflora in Mexico and is very distinctive at its northern limit in the United States. Although P. sparsiflora is exceedingly variable in floral dimensions, in habit, and in the number, size, and placement of leaves, the pattern seen in P. brevifolia seems to lie outside this range of variation. With a generally longer spur and very different ecologic requirements, it is here treated at the specific level. Nonetheless, P. brevifolia is reported to intergrade with P. sparsiflora in Mexico (R. McVaugh and W. R. Anderson. 1974+, vol. 16, pp. 254–256), yet the latter species probably does not range there beyond a possible occurrence in Baja California (M. A. Soto 1988).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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