Wood Fern or Triangular Wood Fern (Dryopteris spinulosa, var. dilatata). 1. Frond, illustrating outline. 2. Enlarged sketch of pinna (underside) illustrating its character and position of sori. 3. Diagramatic sketch illustrating general outline of frond.

TRIANGULAR WOOD FERN.
(Dryopteris spinulosa var. dilatata. (Hoffm.) Kuntze)

The common name of this plant is derived from the broad triangular form of the fronds. It is a rather common fern in the deep woods of the Canadian zone. The habitat it prefers is the moist, shaded forests in humid soils, often found as an associate of the Lady or Swamp Fern. It may be readily distinguished from this plant, however, by the triangular outline of its fronds. Its botanical range includes Alaska, Yukon and east to Greenland; south to California and New Mexico and east to Iowa and in North Carolina. Locally its range is from the lower park boundaries to about 4500'. Its appearance is that of a loose graceful tuft, the fronds 2-3 compound, triangular in outline being about 4-15 inches wide across the basel pinnae; leafstalk and foliate portions of the frond about 12-40 inches in length. It is a herbaceous plant. The leafstalk is as long to half as long as the foliate portion of the frond, generally greenish though sometimes brown or straw-colored and possessed of numerous brown scales. The largest pinnae are short stalked; smaller pinnae near the apex decurrant on the stem; pinule segments sessile and with deeply cleft mucrenate or falcate lobes. Spores are borne in rather small, round sori which are subterminal on the veins; indusium present. Rhizome stout, woody, creeping or ascending.

SYNONYMS: Dryopteris dilatata (Hoffm.) Gray; Aspidium campylopterum Kuntze; Nephrodium dilatatum Desv.; Lastrea dilatata J. Sm.; Aspidium spinulosum var. dilatatum Hoffm.; Nephrodium spinulosum var. fructorum Gilb.; Thelypteris spinulosa var. dilatata St. John.

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