Jepson eFlora: Taxon page
Vascular Plants of California
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Athyrium distentifolium var. americanum

Higher Taxonomy
Family: AthyriaceaeView Description 
Habit: Perennial herb in soil [on rocks]; rhizome short- to long-creeping or tree-like. Leaf: generally tufted or short-spaced, 5--200+ cm, generally +- alike; stipe firm or fleshy (easily crushed), base darker or not, with 2 vascular strands, often expanded at base ("trophopods"); blade generally 1--3-pinnate, +- glabrous or with hairs, hair-like scales, or gland-tipped hairs on axes, veins generally free (or netted); rachis, costa generally grooved adaxially. Sporangia: sori linear along veins, sometimes appearing round; indusia 0 or linear or J-shaped (round), opening away from the vein, when linear, generally back-to-back along a vein.
Genera In Family: 3--5 genera, +- 600 species: worldwide, especially tropics, wooded areas. Note: Comprises three diverse genera (mostly temperate Athyrium, Deparia; mostly tropical Diplazium), and smaller genera often segregated from Athyrium (Anisocampium, Cornopteris; Rothfels et al. 2012 Taxon 61:515--530). One of the most diverse families of the eupolypods II clade (suborder Aspleniineae; Pteridophyte Phylogeny Group 1 2016 J Syst Evol in press); most closely related to Blechnaceae and Onocleaceae (Rothfels et al. 2012 Syst Biol 61:490--509), and more distantly to Woodsiaceae, where often included (Smith et al. 2016 Taxon 55:705--731).
eFlora Treatment Author: Carl J. Rothfels & Alan R. Smith
Scientific Editor: Bruce G. Baldwin & Thomas J. Rosatti.
Genus: AthyriumView DescriptionDichotomous Key

Common Name: LADY FERN
Habit: Rhizome short-creeping to suberect, stout. Leaf: stipe stout, fleshy, easily crushed, straw-colored except base generally blackened, base scaly, ×-section with 2 crescent-shaped vascular strands; blade generally >= 2-pinnate, pinnae of equal sides, +- glabrous or minutely hairy, veins free. Sporangia: sori +- round, +- oblong, or J-shaped; indusia 0, oblong, J-shaped, or reniform, laterally attached.
Etymology: (Greek: doorless, from enclosed sori)
eFlora Treatment Author: Carl J. Rothfels & Alan R. Smith
Athyrium distentifolium Opiz var. americanum (Butters) Cronquist
Leaf: blade narrow-elliptic or lanceolate, 2--3-pinnate, lower 1 or 2 pinna pairs generally +- < those above, ultimate segments shallowly to deeply pinnately lobed, midribs below glabrous or with scattered scales. Chromosomes: 2n=80.
Ecology: Moist or wet rock crevices, talus, cliffs, boulder bases, streamsides; Elevation: 1700--3700 m. Bioregional Distribution: KR, CaRH, SNH, Wrn, W&I; Distribution Outside California: to Alaska, western Canada, Montana, Colorado; also eastern Can, Greenland, eastern Asia. Note: Athyrium distentifolium var. distentifolium in Eurasia.
Synonyms: Athyrium alpestre Milde var. americanum Butters illeg.
Jepson eFlora Author: Carl J. Rothfels & Alan R. Smith
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)

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Botanical illustration including Athyrium distentifolium var. americanum

botanical illustration including Athyrium distentifolium var. americanum

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Citation for this treatment: Carl J. Rothfels & Alan R. Smith 2016, Athyrium distentifolium var. americanum, in Jepson Flora Project (eds.) Jepson eFlora, Revision 4,, accessed on February 28, 2024.

Citation for the whole project: Jepson Flora Project (eds.) 2024, Jepson eFlora,, accessed on February 28, 2024.

Athyrium distentifolium  
var. americanum
click for enlargement
©1995 John Game

More photos of Athyrium distentifolium var. americanum
in CalPhotos

Geographic subdivisions for Athyrium distentifolium var. americanum:
KR, CaRH, SNH, Wrn, W&I
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).


Data provided by the participants of the  Consortium of California Herbaria.
View all CCH records
All markers link to CCH specimen records. The original determination is shown in the popup window.
Blue markers indicate specimens that map to one of the expected Jepson geographic subdivisions (see left map). Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.

CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time (fruiting time in some monocot genera).