[Illustration:  Fragrant Fern. Aspidium fragrans (Mt.  Mansfield.  Vt.)]

KEY TO THE WOOD FERNS

ASPIDIUM

Fronds pinnate, the pinnae pinnatifid;
    Blade soft and thin, not evergreen;
        Lower pinnae reduced to mere lobes
                                                   New York Fern
        Lower pinnae but slightly reduced;
            Veins simple......................Massachusetts Fern
            Veins forked..............................Marsh Fern

Blade rather thick (subcoreaceous) mostly evergreen;
Fronds small, narrow, glandular, rock species
Fragrant Fern
Fronds large, two or more feet high;
Lower pinnae short, broadly triangular
Crested Shield Fern
Lower pinnae longer;
Sori close to the margin....  Marginal Shield Fern
Sori nearer the midvein;
Frond lanceolate....................Male Fern
Frond ovate..............Goldie’s Shield Fern

Fronds twice pinnate with the lower pinnules pinnatifid
                                              Boott’s Shield Fern

Fronds nearly thrice pinnate................Spinulose Shield Fern

[Illustration:  Marginal Shield Fern. Aspidium marginale]

THE WOOD FERNS

The ferns of this group, not counting the small fragrant fern, prefer the woods or at least shady places.  Although the genus Polystichum represents the true shield ferns, the wood ferns are also thus designated, as their indusia have nearly the shape of small, roundish shields.  The old generic name for them all was Aspidium (meaning shield), first published in 1800.  For a long time its chief rival was Nephrodium (kidney-like), 1803.  Many modern botanists have preferred the earlier name Dryopteris (1763), meaning oak fern, alluding, perhaps, to its forest-loving habits.  THELYPTERIS, still earlier (1762), may supersede the others.

[Illustration:  Marginal Shield Fern.  Aspidium marginale (From Woolson’s “Ferns,” Doubleday, Page & Co.)]

[Illustration:  Sori of Marginal Shield Fern]

(1) MARGINAL SHIELD FERN, EVERGREEN WOOD FERN

Aspidium marginale.  THELYPTERIS MARGINALIS Dryopteris marginalis.  Nephrodium marginale

Fronds from a few inches to three feet long, ovate-oblong, somewhat leathery, smooth, twice pinnate.  Pinnae lanceolate, acuminate, broadest just above the base.  Pinnules oblong, often slightly falcate, entire or toothed.  Fruit-dots large, round, close to the margin.  Rocky hillsides in rich woods, rather common throughout our area.  The heavy rootstock rises slightly above the ground and is clothed at the crown with shaggy, brown scales.  Its rising caudex, often creeping for several inches over bare rocks, suggests the habit of a tree fern.  In early spring it sends up a graceful circle of large, handsome, bluish-green blades.  The stipes are short and densely chaffy.  No other wood fern endures the winter so well.  The fronds burdened with snow lop over among the withered leaves and continue green until the new ones shoot up in the spring.  It is the most valuable of all the wood ferns for cultivation.