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FNA | Family List | FNA Vol. 26 | Orchidaceae | Platanthera

6. Platanthera dilatata (Pursh) Lindley ex L. C. Beck, Bot. North. Middle States. 347. 1833.

Orchis dilatata Pursh, Fl. Amer. Sept. 2: 588. 1814; Habenaria dilatata (Pursh) Hooker; Limnorchis dilatata (Pursh) Rydberg

Plants 11–130 cm or more. Leaves few–several, ascending to recurved-spreading, scattered along stem, gradually reduced to bracts distally; blade linear, linear-lanceolate, oblong, or oblanceolate, 3.5–32 × 0.3–7 cm. Spikes very lax to very dense. Flowers resupinate, rather showy, conspicuous, white; lateral sepals spreading to reflexed; petals ovate- to linear-lance-falcate, margins entire; lip descending or apex adhering to dorsal sepal and petal apices, linear-lanceolate to lanceolate, without basal thickening, 4–11 × 2–5 mm, base slightly rounded-dilated to orbiculate, rarely rhombic, margins entire; rostellum lobes parallel to slightly divergent, directed downward, very small, obscure, rounded; pollinaria straight; pollinia remaining enclosed in anther sacs; ovary rather slender to stout, 5–15 mm. 2n = 42.

Varieties 3 (3 in the flora): North America.

An intense clove scent distinguishes Platanthera dilatata from related species across most of its range, but in the far northwest a more complex blend of spicy fragrances predominates.

1 Spur shorter than lip, clavate to slightly capitate.   6b var. albiflora
+ Spur nearly equaling to exceeding lip, slender to slightly clavate.   (2)
2 (1) Spur about equal to lip (mostly within 2 mm).   6a var. dilatata
+ Spur markedly exceeding lip (commonly 11/2 or more times length of lip).   6c var. leucostachys


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