Margin of the indusium denticulate and beset with minute, stalked glands.
In woods nearly everywhere--our most common form. Millions of fronds of
this variety are gathered in our northern woods, placed in cold storage and
sent to florists to be used in decorations.[A] As long as the roots are not
disturbed the crop is renewed from year to year, and no great harm seems to
result. Canada to Kentucky and westward.

[Footnote A: _Horticulture_ reports that twenty-eight million fern leaves
have been shipped from Bennington, Vt., in a single season; and that nearly
$100,000 were paid out in wages.]

[Illustration: Spinulose Shield Fern. _Aspidium spinulosum_ (Maine, 1877,
Herbarium of Geo. E. Davenport)]

[Illustration: _Aspidium spinulosum_, var. _intermedium_]

[Illustration: _Aspidium spinulosum_, var. AMERICANUM]

A tripinnate form of this variety discovered at Concord, Mass., by Henry
Purdie, has been named var. CONCORDIÀNUM. It has small, elliptical,
denticulate pinnules and a glandular-pubescent indusium.

Var. AMERICÀNUM (=_dilatàtum_, syn.). Fronds broader, ovate or
triangular-ovate in outline. A more highly developed form of the typical
plant, the lower pinnæ being often very broad, and the fronds tripinnate.
Inferior pinnules on the lower pair of pinnæ conspicuously elongated. A
variety preferring upland woods; northern New England, Greenland to the
mountains of North Carolina, Pennsylvania, Michigan and northward.