Pyrola asarifolia
Ericaceae subfam. monotropoideae
bog wintergreen, common pink wintergreen, large wintergreen, liver-leaf wintergreen, pink pyrola, pink shinleaf, pink wintergreen, pyrole à feuilles d'asaret
absent, or erect or decumbent.
petiole (6–)15–65(–109) mm, channeled adaxially, glabrous;
blade not maculate, dull and light green to purplish abaxially, shiny and dark green adaxially, ovate, elliptic, round, or reniform, (10–)24–71(–98) × (10–)13–49(–83) mm, coriaceous, base cordate or rounded to decurrent, margins entire or crenulate or denticulate, apex obtuse to acute.
absent or persistent, sometimes scalelike, often much reduced, cauline and alternate or in basal rosettes or pseudoverticillate;
petiole present or absent;
blade plane or acicular, abaxial groove absent.
1 per stem, 4–29-flowered;
peduncular bracts 1–3(–5), ovate to oblong-ovate, 7–16 × 2.5–5 mm, chartaceous or membranous, margins entire;
inflorescence bracts ovate to oblong-ovate, usually as long as or longer than, sometimes shorter than subtended pedicels, 3–17 × 1–3.6 mm, chartaceous.
terminal racemes, umbels, corymbs, cymes, or solitary flowers;
perulae absent;
bracts shorter than, as long as, or longer than sepals.
(3–)4–11 mm.
calyx lobes appressed or spreading in fruit, green or pinkish with margins hyaline to white or pinkish, triangular to triangular-ovate, 1.4–5.5(–5.8) × 1.3–2.7 mm, margins entire or erose-denticulate, apices acute to acuminate;
petals white, white proximally and pinkish distally, or pink to purplish red throughout, obovate to round, 4.8–9.1 × 2.9–6 mm, margins entire;
stamens 4.5–7.5 mm;
filament base 0.6–1.1 mm wide;
anthers (1.7–)2–3.5(–3.9) mm, apiculations 0.1–0.5(–0.7) mm, thecae creamy white or tan to dark pink, tubules pink to dark pink, 0.1–0.4 mm, gradually narrowed from thecae, lateral walls touching for most of their lengths, pores 0.1–0.2 × 0.05–0.1 mm;
ovary smooth;
style exserted, 7–10 mm;
stigma 0.7–1.6 mm wide, lobes erect, (without subtending ring of hairs).
radially symmetric to slightly bilaterally symmetric, horizontal, nodding, or spreading to erect;
sepals absent or 2-5(-6);
petals (3-)4-5(-6), connate or distinct, corolla deciduous or persistent, rotate, crateriform, cylindric, urceolate, or campanulate, if petals connate, lobes shorter than tube;
intrastaminal nectary disc present or absent;
stamens 8-10(-14);
anthers dehiscent by slits or pores;
ovary 1- or (4-)5(-6)-locular;
placentation axile or parietal;
style straight or declinate.
capsular, dehiscence loculicidal or indehiscent to irregularly dehiscent, or baccate and indehiscent.
depressed-globose, 4–5 × 6–8 mm.
25-1000+, distinct, fusiform or ovoid, winged or not.
= 46.
Pyrola asarifolia
Ericaceae subfam. monotropoideae
Subspecies 3 (2 in the flora).
Regional variation in Pyrola asarifolia in North America was examined by E. Haber (1983) using morphological and flavonoid data. Despite finding some longitudinal geographic differentiation, he concluded that most earlier-recognized segregates of the P. asarifolia complex were best included within a single, polymorphic species, with the large-bracted, denticulate-leaved, Pacific Northwest and northern Rocky Mountains element (subsp. bracteata) distinguishable from the relatively short-bracted, crenate-leaved, transcontinental element (subsp. asarifolia). Included within his concept of the latter subspecies were Asian plants referred to P. incarnata (de Candolle) Freyn. A more comprehensive study of the Asian element (Haber and Hiroshi Takahashi 1988) led to the conclusion that this vicariad was sufficiently distinct to warrant recognition as P. asarifolia subsp. incarnata (de Candolle) Haber & Hir. Takahashi; it is distinguished from the North American subspecies by its narrower sepals. Takahashi (1993) found differences also in the seeds of the two subspecies.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Genera 14, species ca. 50 (12 genera, 21 species in the flora).
Two strictly Asiatic genera in the subfamily, Cheilotheca Hooker f. and Monotropastrum Andres, each contain two species.
A persistent error, that heterotrophic members of the Monotropoideae are saprophytic, was disproved by E. Björkman (1960), supported by T. E. Furman and J. Trappe (1971). These plants are considered epiparasitic, deriving their nutrition from coniferous or fagaceous hosts through mutually shared fungal associates. This mode of nutrition also is called mycoheterotrophy. Mycorrhizal associates of several genera have been investigated by K. W. Cullings et al. (1996) and M. I. Bidartondo and T. D. Bruns (2001, 2002).
Inflorescences, the only above-ground structures for these heterotrophic plants (excluding achlorophyllous forms of Pyrola), emerge from soil each year. One or more inflorescences develop from each perennial root system. Because the root systems may branch, it is generally not possible to determine whether any two inflorescences in proximity are derived from the same system. Thus, counting inflorescences as a measure of population sizes is essentially meaningless but may be an indication of the overall health of the plants and recent environmental conditions.
Conclusive distinctions among bracts and similar-appearing appendages without flowers in their axils are generally lacking. The latter are here called sterile bracts. Bracts and sterile bracts are generally similar in their sizes and shapes, but in some taxa sterile bracts are more appressed to the inflorescence axes or are conspicuously more succulent. Because similar structures occur in inflorescences of other Ericaceae and are uniformly sessile, it is difficult to justify calling these structures leaves.
Chlorophyllous members of the subfamily produce three types of similar, bractlike structures. Persistent bud scales, produced in winter buds at the end of each growing season, usually alternate with leaves at the base of the peduncle (H. F. Copeland 1947). Peduncles in all genera except Chimaphila bear up to five bracts, which sometimes subtend aborted flower buds. Individuals of nearly all species occasionally lack peduncular bracts. The pedicel of each flower (absent in Moneses) typically is subtended by a single bract. These inflorescence bracts are free from the pedicel in Orthilia and Pyrola; they are adnate proximally to the pedicel in Chimaphila, the bract thus appearing to arise from the pedicel. Bracteoles are absent.
Pollination studies of some species indicate that chlorophyllous members are largely outcrossing and entomophilous (H. B. Lovell and J. H. Lovell 1936; L. C. W. Jensen 1961; J. T. Knudsen and J. M. Olesen 1993). Knudsen and Olesen found the floral morphology of Chimaphila to be optimized for pollination by large, nectar-gathering insects, especially bumblebees. Moneses, which produces no nectar, is buzz-pollinated by pollen-gathering insects. Orthilia produces nectar and is visited by both nectar- and pollen-gathering insects. Pyrola produces no nectar and is buzz-pollinated.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Margins of leaf blades entire or crenulate; proximal inflorescence bracts usually as long as or longer than subtended pedicels, sometimes shorter than subtended pedicels; calyx lobe apices acute to acuminate; leaf blades round, ovate, elliptic, or reniform. | subsp. asarifolia |
1. Margins of leaf blades denticulate or, rarely, entire; proximal inflorescence bracts longer than subtended pedicels; calyx lobe apices acuminate; leaf blades ovate or elliptic. | subsp. bracteata |
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