LEAVES: widely spaced along the rhizome, 0.4–3.5 m long. PETIOLES: straw-colored, hairy at least proximally. RACHISES: similar to petioles, straw colored to green, glabrous or hairy. BLADES: 15–100 cm wide, broadly deltate, mostly 3-pinnate-pinnatifid, with usually 14 or fewer main lateral pinnae, these often opposite or nearly so along the rachis, the basal few pairs of pinnae longer basiscopically than acroscopically PINNAE: 7–50 cm long, mostly 2–5 times as long as wide, the pinnules with numerous deep lobes, sparsely to densely hairy, at least abaxially (Fig. 2A). LOBES: with the margins entire or inconspicuously crenulate. PSEUDOINDUSIA: differentiated from the rest of the blade, pale or whitened, glabrous or hairy. SPORES: 25–40 μm long, the surface finely granulate, dark brown. 2n = 104. NOTES: Nearly worldwide. Bracken is found on every continent except Antarctica and generally is considered one of the world’s worst weeds, which render range land unsuitable for grazing. Toxins contained in the leaves inhibit the growth of other plant species, and the species has been shown to interfere with the regeneration of trees and shrubs following fires or logging in the western United States. Although the developing fiddleheads have been harvested for human consumption, the leaves also contain a number of nerve toxins, as well as carcinogenic and mutagenic compounds, that are poisonous to both livestock and humans when ingested. REFERENCES: G.Yatskievych and M.D. Windham , 2008, Vascular Plants of Arizona: Dennstaedtiaceae. CANOTIA 4 (2): 38–40.