Perennial fern ally 30 - 60 cm tall Leaves: stalkless on branchlets, and in four ranks: top, bottom, and sides (lateral). The top rank of leaves (i.e. along branchlet upper side) are appressed and narrowly lance-shaped to somewhat linear with slender tips, the lateral ranks of leaves are similarly shaped but may be appressed or spreading, but the bottom rank of leaves (i.e. along branchlet underside) are wide spreading though weakly developed, very reduced, and hair-like. Rhizome: buried under soil surface, rounded to almost flattened in cross-section, 1.3 - 3.2 mm in diameter, and covered with small, thin, appressed to ascending, scale-like leaves. Spores: hundreds per sac, all of one kind, 20 - 40 microns in diameter, thick-walled, veiny, and three-sectioned (trilete) with pointed angles. The spores give rise to the gametophyte (the sexual phase of the plant), which is small (no more than 3 cm long), carrot-shaped, underground, not green, but saprophytic, and inhabited by symbiotic fungi (mycorrhizae). Upright stems: arising from rhizomes, branching, mostly rounded in cross-section, and covered with small, awl-shaped, appressed leaves. Branchlets: lateral from upright stems, ascending, flattened, almost blade-like, only up to 2 mm wide. The branchlets successively branch twice, and subsequently become somewhat fan-shaped.
Similar species: Diphasiastrum x habereri is very similar to both its parent species, D. digitatum and D. tristachyum. The key differences in D. digitatum are that its rhizomes are located on the surface of the soil and never buried, it tends to be a bit shorter (15 - 55 cm), and its ultimate branchlets are wider (3 - 4 mm wide). The key differences for D. tristachyum are that it has cordlike, nearly four-angled ultimate branchlets; the leaves on the underside of the branchlets are well-developed and fairly similar in size and shape to the other ranks of leaves; and the strobili never have sterile areas at the tips.
Habitat and ecology: Unknown exactly, but presumably somewhat rare except for the eastern part of the Chicago Region where both parent species occur.
Occurence in the Chicago region: native
Notes: This hybrid has been quite overlooked and often confused with both parent species in areas where they overlap (Wagner and Beitel 1993). Part of the problem is that the hybrid has characters that are very intermediate between both parents, and one must look at all relevant characters rather than basing an identification on only one or two characters.
Etymology: Diphasiastrum comes from the Latin Diphasium, the name of a genus, and astrum, meaning "incomplete resemblance". Habereri is named after botanist Joseph Valentine Haberer (1855-1925).
Author: The Field Museum
Citation: The vPlants Project. vPlants: A Virtual Herbarium of the Chicago Region. http://www.vplants.org
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