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Key to Diphasiastrum

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1 Vegetative branchlets strongly ascending; strobili usually 1 or 2, borne sessile to, or with a very short peduncle above, a leafy stem; [ne. PA northwards]
1 Vegetative branchlets spreading to somewhat ascending; strobili usually 3 or 4, borne on a remotely-bracted peduncle; [collectively widespread in our area].
  2 Foliage blue-green, glaucous; horizontal branchlets 1-2 mm wide (including the leaves); branchlets with conspicuous annual constrictions; rhizomes (1-) 5-12 cm deep; abaxial rank of leaves on horizontal branchlets as long as the lateral ranks (thus the branchlets more-or-less square in cross-section)
  2 Foliage dark green, not glaucous; sterile branchlets 2-4 mm wide (including the leaves); sterile branchlets without conspicuous annual constrictions; rhizomes 0-1 cm deep (which can be determined by pulling up a single upright shoot – the depth to rhizome is approximately the length of the white portion of the vertical stem); abaxial rank of leaves on horizontal branchlets shorter than the lateral ranks (thus the branchlets flattened in cross-section)
    3 Strobili mostly 10-25 mm long, lacking sterile tips, borne on very slender stalks becoming stramineous in color prior to spore release; peduncles, if present, regularly forked; [widespread northward from SC w. to AR]
    3 Strobili mostly 20-40 mm long, often bearing sterile tips, borne on relatively thicker stalks remaining green until after spore release; peduncles mostly branching abruptly at base, thus producing a false whorl; [n. PA (?) and Sullivan County, NY northward]
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