What’s a dichotomous key?
Help
Dryopteris
See list of 9 species in this genusHybrids in Dryopteris are common in mixed-species populations. Certain hybrid combinations are almost always found when the two parents grow together (e.g., D. ×boottii), whereas others are very rare (e.g., D. ×pittsfordensis) or unknown in the region. Hybrids can be recognized by abortive spores and intermediate morphology. References: Thorne and Thorne (1989), Montgomery and Wagner (1993).
-
1a. Leaf blades mostly 6–25 cm long, with aromatic glands, densely scaly abaxially; indusia often overlapping
-
1b. Leaf blades 15–120 cm long, mostly more than 25 cm, lacking aromatic glands (but sometimes with stipitate glands), with few or no abaxial scales; indusia separate
-
2a. Leaf blades (2–) 2.5- to 3.5-times divided near base; leaf segments with bristle- tipped teeth
-
3a. First basiscopic (i.e., lower) leafule of basal leaflet no longer than adjacent basiscopic leafule and less than 2 times as long as first acroscopic (i.e., upper) leafule of basal leaflet [Fig. 21]; plant axes and indusia with glandular hairs; leaf blades remaining green through the winter
-
3b. First basiscopic leafule of basal leaflet longer than adjacent basiscopic leafule and 2–5 times as long as first acroscopic leafule of basal leaflet [Figs. 19,20]; plants without glandular hairs (rarely with a few glandular hairs in D. campyloptera); leaf blades senescing in the fall
-
4a. First pair of leafules of basal leaflet nearly opposite, not more than 4 mm apart, the basiscopic leafule 2 (–3) times the length of the acroscopic one [Fig. 20]; blade ovate-lanceolate
-
4b. First pair of leafules of basal leaflet offset 4–15 mm, the basiscopic leafule (2–) 3–5 times the length of the acroscopic one [Fig. 19]; blade ovate-deltate
-
-
-
2b. Leaf blades 1.5- to 2-times divided near base; leaf segments with or without bristle-tipped teeth
-
5a. Sori borne at or near margins of leaf segments; leaf blades blue-green; petioles with a dense tuft of white-brown scales at the base
-
5b. Sori borne between margins and midrib of leaf segments; leaf blades green; petioles with scattered light to dark brown scales
-
6a. Plants with scales of 2 distinct types—one broad, one hair-like; scales abundant on petiole, rachis, and costae; leaves with 20–30 pairs of leaflets; petiole length up to 0.25 times the length of the blade
-
6b. Plants with scales of various sizes, mostly broad, but not of 2 distinct sizes; scales abundant on only the petiole; leaves with 10–25 pairs of leaflets; petiole length 0.25–0.35 times the length of the blade
-
7a. Scales of the petiole dark brown to black, with a pale border; sori borne close to midrib; basal leaflets ovate-oblong; teeth of leaf segments not bristle-tipped
-
7b. Scales of the petiole light brown (sometimes dark brown in the center in D. clintoniana); sori borne midway between margin and midrib; basal leaflets triangular to elongate-triangular; teeth of leaf segments bristle-tipped
-
8a. Fertile leaves deciduous, their leaflets twisted, parallel to the horizon, noticeably larger and more erect than the persistent sterile leaves; basal leaflets triangular to broad-triangular
-
8b. Fertile leaves persistent, their leaflets not twisted, parallel to the leaf axis, only slightly different from the sterile leaves; basal leaflets narrow-triangular to oblong-triangular
-
-
-
-
-
Show photos of:
Each photo represents one species in this genus.