Platanthera lacera
Platanthera orbiculata
green fringe bog-orchid, green fringe orchid
large round-leaf orchid, large round-leaf rein orchid, lesser roundleaf orchid, round-leaf bog-orchid, round-leaf orchid
1–4, wide-spreading to ascending, scattered along stem, gradually to abruptly reduced to bracts distally;
blade linear-lanceolate, linear-oblong, or oblong-obovate, 7–23 × 0.7–5 cm.
2, in subequal basal pair lying on ground;
bracts (very rarely, 0–)1–6, scattered along stem;
blade broadly elliptic to orbiculate or oblate, 5–21 × 3–22 cm.
lax to dense.
lax to dense.
resupinate, not showy to inconspicuous, whitish green or yellowish green, lip often paler;
lateral sepals reflexed;
petals linear to narrowly oblong-spatulate, margins entire or apex rarely slightly lacerate;
lip descending, without basal thickening, deeply 3-lobed, 10–17 × 13–17 mm, lobes extensively and deeply divided, commonly into filiform divisions, margins rarely merely fringed or middle lobe merely lacerate-fringed, lateral lobes narrowly to broadly cuneate, middle lobe cuneate-flabellate, usually narrow;
spur slenderly to markedly clavate, 11–23 mm;
rostellum lobes nearly parallel, directed downward, short, rounded;
pollinaria nearly straight;
pollinia remaining enclosed in anther sacs;
viscidia linear;
ovary slender to stout, mostly 8–20 mm.
resupinate, rather showy;
calyx mostly greenish white;
corolla mostly white;
lateral sepals reflexed to somewhat spreading;
petals lanceolate-falcate, margins entire;
lip descending to somewhat reflexed, linear-oblong to linear-lanceolate, without basal thickening, 7–17 × 1–2.5 mm, margins entire;
spur slenderly clavate, 14–27 mm;
rostellum lobes directed strongly forward, wide-spreading, angular;
pollinaria nearly straight, 3–4.5(–4.8, very rarely) mm;
pollinia remaining enclosed in anther sacs;
viscidia orbiculate;
ovary slender to rather stout, mostly 10–26 mm.
= 42.
= 42.
Platanthera lacera
Platanthera orbiculata
Hybrids with Platanthera grandiflora (P. ×keenanii P. M. Brown; see note under 20. P. grandiflora) and P. psycodes [P. ×andrewsii (M. White) Luer] are variably intermediate between the parents, with various purple-green shadings and lobes of the lip generally narrower and more dissected than in the purple-flowered parents. The linear viscidia of P. lacera and the large anther sacs of P. grandiflora provide means for determination. The ratio of viscidium length/width of 1–3.2 distinguishes hybrids and purple-flowered parents from P. lacera, which is characterized by a ratio of 2.7–4.6. The parentage of hybrids can be determined by different sized anther sacs: P. ×andrewsii, 1.4–2.3 mm; P. ×keenanii, 2.5–4.2 mm. Those hybrids can be distinguished from their purple-flowered parents by less intense coloring and the ratio of viscidium length/width: P. psycodes 1–1.5; P. ×andrewsii, 1.3–3; P. grandiflora, 1–1.5; P. ×keenanii, 1.5–3.2. The plants known as Platanthera lacera var. terrae-novae (Fernald) Luer (Habenaria lacera var. terrae-novae Fernald) apparently represent swarms of P. ×andrewsii and introgressed P. lacera (P. M. Catling and V. R. Catling 1994).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The key will permit determination of most specimens of Platanthera orbiculata and P. macrophylla. More precise discrimination of ambiguous specimens is possible by use of the formula from A. H. Reddoch and J. M. Reddoch (1993): spur length + (2 × pollinarium length), which for P. orbiculata is less than 38 and for P. macrophylla is equal to or greater than 38.
Considerable variation in size and shape of leaves occurs, and although to some extent regional in nature, intergradation is complete; recognition of infraspecific taxa is unwarranted. A few collections from isolated areas on the Pacific Coast of Canada are noteworthy, however. Those are small, few-flowered plants with rather narrow leaves borne alternately or suboppositely toward the base of the stem, as in some Asiatic species. They are in some respects very similar to Platanthera freynii Kränzlin, an Asiatic species distinguished primarily by its abruptly narrowed petals, in contrast to the generally broader, but variable, petals in North American plants. These western plants warrant further study to establish their identity and to elucidate relationships between North American and Asiatic species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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