This genus was placed in the Pyrolaceae in Michigan Flora.
1. Style straight, ca. 1.8 mm or less long; flower clearly with radial symmetry.
1. Style ± strongly bent downward, (4–) 5–9 (–9.5) mm long at anthesis and on fruit; flower slightly bilaterally symmetrical.
2. Leaf blades thin, dull above, elliptic-oblong, distinctly longer than their petioles; calyx lobes 1–1.8 (–2.5) mm long, deltoid; bracts of the raceme narrowly cuneate, less than 1 mm broad; anthers hardly if at all constricted beneath the pores; petals white.
2. Leaf blades thick, ± leathery, ± shiny above (or distinctly shorter than their petioles), nearly or quite orbicular (occasionally broadly elliptic); calyx lobes various (if less than 1.8 mm long, the leaf blades usually shorter than the petioles); bracts of the raceme mostly over 1 mm broad (except sometimes in P. chlorantha); anthers abruptly contracted to distinct short tubes beneath the pores; petals white to greenish or pink.
3. Calyx lobes 1–1.5 (–1.7) mm long and mostly a little broader; leaf blades dull, all or mostly shorter than their petioles (or leaves absent); petals greenish white; major bracts at base of stem (among the leaves) less than 6 mm long.
3. Calyx lobes (1.3–) 1.5–3.2 (–4) mm long and equally broad or (usually) distinctly longer than broad; leaf blades shiny above, shorter to longer than the petioles; petals white to pink or reddish; major bracts at base of stem over 6 mm (often over 10 mm) long.
4. Petals white (very rarely pinkish); calyx lobes ± ovate-oblong with ± curved sides, not overlapping at base; leaf blades rounded to nearly truncate at the base (± tapered-decurrent onto the very narrowly winged petiole).
4. Petals pink to reddish (rarely white); calyx lobes ± triangular with straight sides, mostly slightly overlapping at the very base [10–20×]; leaf blades rounded to subcordate or cordate at the base (only shortly if at all decurrent).