Nature Notes

Vol. XV March - 1937 No. 1

Field Key to the Ferns of Mt. Rainier Nat'l Park


Plants fern-like, moss-like, rush-like or aquatic in general character; annual or perennial. Reproduction by spores with sporophyte generally possessed fibrous roots. Stems, leaves and roots with vascular tissue.


1-Plants not fern-like... 2.
1-Plants generally fern-like and often with compound leafstalks ... 13.
2-Stems hollow, round, ridged and conspicuously jointed; joints covered by toothed sheaths; spores borne in sporangia on scales of terminal, dry, cone-like spikes. Leaves united into sheath-like whorls about the stem at the joints. Stems sandy or minutely roughened to the touch
... 3.
2-Stems without conspicuous joints and otherwise not as described above
... 6.
3-Aerial stems evergreen, perennial; spore bearing and non-spore bearing stems alike in appearance; grooves and ridges very rough. Found in most soils having ample moisture; stems 1-1/2 - 6 feet tall. COMMON SCOURING RUSH (Equisetum hyemalea)
3-Aerial stems not evergreen ... 4.
4-Aerial stems all green and essentially alike; fertile stems branched with numerous whorls of branches; grows in very wet soils or in water; 18 - 36 inches tall. SWAMP HORSETAIL (Equisetum limosum)

4-Aerial stems of two kinds - spore bearing and non-spore bearing
... 5.
5-Aerial stems annual; 4-18 inches tall. Sterile stems green and having whorled branches at the joints. COMMON or FIELD HORSETAIL (Equisetum arvense)
5-Aerial stems annual; 1-1/2 to 9 feet tall. Sterile stems ivory-grey, green or brownish. GIANT HORSETAIL (Equisetum telmateia)
6-Stem elongate, creeping (sometimes underground) or branching. Leaves small, with axillary sporangia, short, crowded and closely overlapping or scale-like on the stem
... 8.
6-Leaves long and linear; grass-like or awl shaped and overlapping one another at the base and forming a rosette in a single basal tuft. Stem short and onion-like. Two kinds of spores (microspores and megaspores) a conspicuous feature; both types borne in sporangia that are sessile and somewhat sunken in the base of the leaf on the inner side. Found in boggy soils or partly submerged at the edges of ponds or lakes.
... 7.
7-Plants growing where they are submerged during only a part of the year. BRAUN's QUILLWORT (Isoetes braunii).
7-Plants growing where they are submerged during the entire year. BOLANDER's QUILLWORT (Isoetes bolanderi).
8-Sporangia of two kinds, some containing many minute spores (microspores) and the others bearing fewer but larger spores (megaspores). Spore leaves not differing greatly from the foliage leaves and forming small terminal spikes or cone-like structures. SELAGINELLA (Selaginella wallacei).

8-Sporangia containing but one kind of spores. Sporophylls elongated so that the leaves on that part of the plant are widely scattered and not overlapping; sporophylls generally in erect spike or cone-like structures (except L. selago)
... 9.
9-No cone-like structures present; sporangia in the axils of ordinary leaves; creeping stem short or sometimes nearly absent; erect branches often several in a tuft; leafy branches densely tufted. FIR CLUB MOSS (Lycopodium selago).
9-Cone-like structures present and sporangia in axils of modified cone leaves only; creeping stems very evident. ... 10.
10-Leaves bristle tipped, edges of leaves minutely toothed; cones one to two inches long. CLUB MOSS or GROUND PINE (Lycopodium clavatum)

10-Leaves not bristle tipped
... 11.
11-Prostate stems not over 18 inches long; erect leafy branches round in cross section; cone bearing branches bear a single cone only; cone up to one inch long. ALASKAN CLUB MOSS (Lycopodium sitchense).
11-Prostate stems more than 18 inches long ... 12.
12-Cones up to 1-1/2 inches long; prostrate stems up to 2 yards long; erect leafy branches up to 12 inches long; leaves pointed sharply but without bristle point. STIFF CLUB MOSS (Lycopodium annotinum).

12-Cones up to 5 inches long; cone bearing branches obviously different from other branches; prostrate stem up to 3-1/2 yards long; cone bearing branches bearing several cones. CLUB MOSS or GROUND CEDAR (Lycopodium complanatum).

13-Spore-bearing part bladeless and not frond-like, appearing to arise from the leaf stalk of a foliage leaf. Leaves one-to three-compound, the foliate part de-compound. Sporangia large and in grape-like bunches, opening by transverse slits to release the numerous sulphur-yellow spores. Roots fleshy; small to medium sized plants... 14.
13-Plants typically fern like; fronds simple to de-compound. Spore leaves like or unlike the foliage leaves and bearing spores in sporangia on the back or margins of the pinnae or their divisions. Sporangia appear as dots or rows of brownish sori... 16.
14-Length of stem (peticle) below junction with leaf not exceeding one inch. SIMPLE GRAPE FERN (Botrychium simplex).

14-Length of stem (petiole) below the junction with the leaf more than one inch
... 15.
15-Leaf one or two pinnately compound; leaf segments broad and margins rounded. GRAPE FERN (Botrychium pinnatum).
15-Leaf blade with pointed or lance-like pinnae. LANCE-LEAVED GRAPE FERN (Botrychium lanceolatum).
16-Fronds distinctly of two kinds
... 17.
16-Fronds not distinctly of two kinds; spore bearing fronds the same as non-spore bearing fronds in appearance
... 18.
17-Plant (except reproductive fronds) evergreen; vegetative fronds in a rosette on the ground with reproductive fonds upright. Vegetative fronds 2-4 inches wide and 12-24 inches long; pinnae sessile with entire margins. Reproductive fronds 16-40 inches long and 1-3 inches wide with pinnae distantly spaced on the stem and very narrow. Common in moist, shaded woods. DEER FERN (Struthiopteris spicant).
17-Plant not evergreen; 6-12 inches tall. On or among rocks and generally dry soils. Foliage much divided, densely tufted and "parsley-like" in general appearance. Spore bearing fronds taller than non-spore bearing fronds. Sori borne under recurved margin of fertile pinnae. ROCK BRAKE or PARSLEY FERN (Cryptogramma acrostichoides).
18-Spores borne in sori beneath recurved leaf margins
... 19.
18-Spores not borne beneath recurved leaf margins as in above; sori plainly visible on underside of pinnae as brownish dots
... 21.
19-Leaf margins recurved along entire length... 20.
19-Leaf margin recurved only at intervals and where sori are found; plant rather delicate and feathery in appearance with fronds tufted and dichotomously branched. Stems slender, dark brown and shiny in appearance as if varnished. Pinnae attached to stem by slender petiole; palmately veined. In ravines and rocks. MAIDENHAIR FERN (Adiantum pedatum var., aleuticum).
20-Plant stiff and coarse in appearance; not tufted. Fronds harsh and brittle to the touch, usually 3 compound and with silky grey pubescence or underside. Fronds 3-6 feet tall, greenish and stout. Pinnules sessile or occasionally short stalked and with entire margins. In poorer soils, especially on burned areas. BRAKE or BRACKEN (Pteridium aquilinum, var. languginosum).

20-Plant short, densely tufted. Fronds 4-14 inches long, pinnately two and, occasionally, three compound. Underside of pinnae brown and fuzzy. In dry and rocky situations. LACE FERN (Choilanthes gracillima).

21-Plant distinctly tufted... 22.
21-Plant not tufted or not distinctly so... 31.
22-Pinnae 1-2 compound and sharply serrate with numerous pointed saw-edge teeth; pinnae unequal at base with upper side larger; pinnae attached to stem by slender petiole. Fronds evergreen and of general leathery texture; leaf stalks with brown scales at base
... 23.
22-Pinnae not sharply serrate with pointed and conspicuously barbed teeth or, if serrate, the teeth being of a more ragged appearance and not of uniform saw-edge character
... 24.
23-None of pinnae compounded a second time... 25.
23-Basal pinnae compounded a second time; fronds 16-40 inches long, lanceolate elliptic in outline, being widest between the base and middle of the frond. Pinnules sessile and margined with numerous sharp, bristle-tipped teeth. BRISTLE FERN or VANCOUVER FERN (Polystichum andersoni).
24-Fronds 6-24 inches long and 1-3 inches wide at the widest part (just above middle) and tapering toward either end. Pinnae 1/4-1/2 inch wide and 3/4-1 inch long, holly-like in appearance and texture with margins of prickly teeth; larger teeth interspersed with smaller serrations. Evergreen. HOLLY FERN (Polystichum lonchitis).

24-Fronds 12-60 inches long, linear-lanceolate in outline and leathery in texture; widest at base to middle, being 2-10 inches wide at widest point. Pinnae long and linear, 1/4 inch wide and 3 inches long being about average. Teeth recurved. Leaf stalk scaly with numerous brown linear scales. Common in deep moist woods. Evergreen. SWORD FERN (Polystichum munitum).

25-Fronds very narrow and linear in outline, 1/3 to 1 inch wide and 2-10 inches long; densely tufted and generally in bunches nearly as wide as tall; fronds are compound. Pinnae bright green, round-oblong or oval with crenulate (wavy) margins; square at base and attached to the stem by a slender petiole. Leafstalks persistent and conspicuous after the pinnae (most of which remain for about a year) drop off. Not common. Found generally among rocks or on cliffs on moist situations; usually in upper Hudsonian or lower Arctic-alpine zones. SPLEENWORT (Asplenium viride).
25-Not as described above. Fronds more than once compound and not linear in outline... 26.
26-Plant small to medium in size; fronds up to 24 inches long but usually 5-10 inches long; tufted but loosely so and spreading; 1-2 compound. Leafstalk brown or straw colored, very slender and fragile; pinnules thin and delicate with veins of pinnules extending to the edge of marginal teeth. Quite common from deep woods to timberline. BRITTLE FERN (Cysbottomteris fragilis).

26-Plants generally larger than the above and ranging from medium to large size; stems of fronds not delicate
... 27.
27-Plant of the Hudsonian zone; among rocks and talus. Fronds deep green, densely bunched and erect or nearly so, pointing stiffly upward from curved leaf stalks. Fronds 8-28 inches long, narrow to oblong-lanceolate in general outline; 1-1/2 - 5 inches wide; pinnately 2-3 compound. Leafstalk short and curving beneath the rocks, rather stout, brown, and with brown scales at the base. ALPINE LADY FERN (Athyrium alpestre var. americanum).
27-Plants of the deep moist woods growing in accumulated duff of the moist forest floor or in rich moist soils along banks of streams or in boggy places ... 28.
28-Fronds triangular in outline, widest at base, 2-3 compound, 12-40 inches long and 4-6 inches wide at widest point. Fronds tufted and wide-spreading. Pinnules margined with rounded, barbed teeth. One of the most common ferns in moist shaded woods. WOOD FERN (Dryopteris spinulosa var. dilatata).

28-Fronds not triangular in outline; either widest at or near the middle
... 29.
29-Fronds 2-3 compound. Plant large, tufted, wide spreading, and with generally erect fronds 1-4 feet long. Margin of pinnules with several small, irregular teeth; pinnules sessile. Leaf stalks short and straw colored at base. Very common in deep moist woods. LADY or SWAMP FERN (Athyrium filix-femina).
29-Fronds once compound... 30.
30-Fronds 12-56 inches long with leafstalk 2-12 inches long. Largest pinnae short stalked and segments of lobes serrate with curved, oblique teeth. Width of fronds, at widest part, 4-12 inches. Fairly common in deep woods. MALE FERN (Dryopteris filix-mas).

30-Fronds 20-36 inches long, elliptic-lanceolate in outline. Leafstalks about 4-12 inches long and about 1/4 as long as the blade, straw-colored and scaly at base. Pinnae sessile and margins entire or crenate (wavy). SIERRA WATER FERN (Dryopteris oregana).

31-Plant with three triangular-shaped pinnae held aloft in a horizontal, or nearly horizontal, plane by slender, delicate stalks 6-10 inches tall. Fronds arise from creeping rootstalks. Fronds of delicate appearance. Margin of lobes crenate (wavy). Common on rich humus in deep, moist woods. OAK FERN (Dryopteris linnaena).
31-Plant not as describe above; commonly growing on rocks, tree trunks and logs, generally in moist situations. Not delicate in appearance. Fronds arising singly from a rhizome; once compound and with pinnae sessile... 32.
32-Fronds 6-18 inches long with 10-35 pairs of lanceolate, acute or attentuate and usually serrulate lobes. LICORICE FERN (Polypodium vulgare).

32-Fronds 2-8 inches long with 7-15 pairs of oblong, obtuse, crenate (wavy) or entire lobes. LICORICE FERN (Polypodium vulgare, var. columbianum).


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