Key to Wisconsin Osmundaceae
Author: Robert W. Freckmann
- 1a.Fertile leaves with all pinnae cinnamon-brown (light brown with yellow-orange tint), lacking expanded flat green pinnae or pinnules; sterile leaves very different in appearance with all pinnae expanded and green; mature sterile pinnae with small tufts of brown hairs at base; pinnules absent, lobes of pinnae often with a small pointed apex Osmundastrum
- 1b.Fertile leaves with green expanded, flat pinnae or pinnules along with smaller pinnae or pinnules bearing sporangia; sterile fronds resemble fertile leaves but lack the smaller fertile pinnae or pinnules; mature pinnae without tufts of brown hairs at base; pinnules present, or pinnae lobed and rounded at apex Osmunda
The Osmundaceae include four genera and about 20 species, although only three genera were recognized in most older works and some recent works recognize six. The Wisconsin flora has three species, until recently all included in Osmunda. Our species are common large ferns, typically on moist or wet soil. Stems (rhizomes) are at about ground level, slowly expanding or creeping (sometimes for several centuries), hard, thick, densely covered by old stipe bases (but no scales) and black fibrous roots, often sold as "osmundine" for growing orchids and epiphytes. The family has the richest fossil record of any fern group, appearing about 250 million years ago in the Permian Period. They were widespread in the Triassic with over 200 species described. Fossils found in a 180-million-year-old Jurassic lava flow in Sweden appear to be identical to living Osmundastrum cinnamomeum, making it the world's oldest known extant plant species.