Osmunda claytoniana
Osmundaceae
interrupted fern, osmonde de Clayton
royal fern family
creeping, beset with old petiole bases and black fibrous roots;
scales absent;
older stems seldom persisting.
pinnate-pinnatifid;
petioles ca. 1/3 length of blades, winged, with light brown hairs, becoming glabrate.
monomorphic or dimorphic.
with greatly reduced, sporangia-bearing medial pinnae that wither early, giving appearance of no middle pinnae (hence the vernacular name, interrupted fern).
elliptic to oblong, ca. 0.5–1 m;
pinnae broadly oblong, lacking persistent tuft of hairs at base; ultimate segments with base truncate, margins entire, apex rounded.
1–2-pinnate (2-pinnatifid);
rachises grooved.
monomorphic or dimorphic.
dichotomous, running to margins.
absent;
sporangia born on slightly modified fertile segments of blades also possessing fully expanded pinnae, or sporangia covering blades lacking green expanded pinnae, clustered in marginal zones, indusia lacking.
greenish, turning dark brown.
green, all alike.
green, aboveground, obcordate to elongate.
of reddish to light brown hairs.
=44.
Osmunda claytoniana
Osmundaceae
Osmunda claytoniana is sparingly cultivated as an ornamental.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Osmundaceae are considered intermediate in several respects between eusporangiate and leptosporangiate ferns. In the absence of sori, simultaneous maturation of spores, and development of sporangia from several initial cells, they are much like eusporangiate ferns. Their large prothalli with projecting antheridia are similar to those of leptosporangiate ferns.
Genera 3, species 16–36 (1 genus with 3 species and 1 hybrid in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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