Blechnum glandulosum Link; B. occidentale sensu auct., non L.

Naturalized

Latin, appendicula, with small appendages or projections, + -atus, a suffix indicating possession. Possibly referring to the short glandular hairs on the rachises.

Plants medium-sized. Rhizomes erect, stoloniferous, stolons subterranean, long-creeping. Fronds 20-60 cm long, clustered at tips of rhizomes, young fronds colored pink to rosy. Stipes about 1/2 frond length, straw-colored, with scattered tan scales in lower parts, well clothed with very short, chainlike hairs. Blades 1-pinnate, lanceo-late to ovate-lanceolate, pinnae well sepa-rated in basal 2/3, gradually becoming pinnatifid at tips; rachises grooved, straw-colored, abaxial surfaces well covered with very small, inconspicuous, 0.1 mm glands, small, short glandular hairs, and stubby round-tipped hairs, abaxial surface with fewer of these structures. Pinnae 6-20 pairs before be-coming pinnatifid near blade tips, short-stalked proximally to adnate distally, ovate-lanceolate, 2.5-8 cm long, basal pinnae smaller or not, margins entire, adaxial costal groove not continuous with rachis groove. Veins joining to form continuous linear veins (commissures) close to and parallel to costae, forking distally. Sori long-linear, on pericostal vein commissures, 1-5.5 cm long, extending most of length of pinnae. Indusia tan, scarious, opening inward.

Common as clones forming large colonies in closed-canopy mesic forests, especially on rock or rocky substrates, and occurring in all but the most extreme habitats, 30-1,560 m, all major islands.

This tropical American fern, first collected in Hawai'i in 1918, has escaped from gardens and spread extensively. It is a serious weed that competes with many native fern species and is especially threatening to species of the rare endemic genus Diellia.

This fern has uniformly been called Blechnum occidentale L. since it was first reported in Hawai'i; however, the rachises of B. occidentale are entirely glabrous but those of B. appendiculatum Willd. are minutely pubescent and glandular, as is the naturalized Hawaiian species. Blechnum appendiculatum Willd., from the American Tropics, is part of the taxonomically difficult B. occidentale complex. A. R. Smith, who is working on re-gional floras of the Central and South America area, has found that the name B. glandulosum Link, which has been used for this fern, must be replaced by the legitimate, older name that has priority, B. appendiculatum Willd.

Blechnum appendiculatum, a colony-forming fern, may be recognized by its 1-pinnate fronds with pinnae having two long sori close to and parallel with the midribs, and stolon-bearing rhizomes.