Homalosorus

Homalosorus is a genus of fern with only one species, Homalosorus pycnocarpos. Commonly referred to as the narrow-leaved glade fern, narrow-leaved spleenwort, or glade fern, it may also be referred to by its older synonyms Athyrium pycnocarpon and Diplazium pycnocarpon. It is endemic to eastern North America and typically grows in rich woodlands. Once classified in the family Athyriaceae due to its linear, often doubled sori, phylogenetic research has shown that it belongs to the small family Diplaziopsidaceae, whose other three species are native to east Asia.

Silvery glade fern
Homalosorus pycnocarpos in rich mesophytic forest, Brown County State Park, Indiana, USA.

Secure  (NatureServe)
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Class: Polypodiopsida
Order: Polypodiales
Suborder: Aspleniineae
Family: Diplaziopsidaceae
Genus: Homalosorus
Small ex Pic.Serm.
Species:
H. pycnocarpos
Binomial name
Homalosorus pycnocarpos
(Spreng.) Pic.Serm.
Synonyms
  • Asplenium pycnocarpon Spreng.
  • Athyrium pycnocarpon (Spreng.) Tidestr.
  • Diplazium pycnocarpon (Spreng.) Broun

Description

Homalosorus pycnocarpos is a tall slender-leaved fern growing as individuals with 5 to 6 leaves. The plant spreads by creeping underground stems allowing a small colony to develop over time. The leaf blade is oblong-lanceolate and once-pinnate. Leaves grow to about 90 cm (36 in) long and 15 cm (6 in) wide. The pinnae are linear and entire. Fertile leaves are similar but erect, narrower than sterile leaves and with longer stipes. The sori are long and narrow in two lines along the underside of a leaf pinna, giving rise to its specific epithet pycnocarpon ('crowded fruits').

Its common name description "narrow-leaved" is reflected in its original specific epithet by André Michaux in 1803: angustifolium (angustus 'narrow' + folium 'leaf'). Michaux classified it in the genus Asplenium.[1]

Distribution

Endemic to eastern North America. Widespread from southern Ontario to the Gulf of Mexico and west to Minnesota and Arkansas. Usually found as isolated plants or colonies. See Flora of North America for distribution map.

Ecology

Grows in lighter parts of mesophytic forests and in ravines in moist but well-drained, neutral to basic soils.

References
  1. Lloyd H. Snyder, Jr.; James G. Bruce (1 October 1986). Field Guide to the Ferns and Other Pteridophytes of Georgia. University of Georgia Press. p. 118. ISBN 978-0-8203-2385-5. Retrieved 26 September 2013.

Further reading
  • Cobb, Boughton. (1984). A Field Guide to Ferns and their Related Families of Northeastern and Central North America. Peterson Field Guides.
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