Lycopodiaceae

• See list of 2 genera in 1a
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  1a. Upright shoots unbranched, lacking winter bud constrictions, produced from horizontal shoots that travel over the surface [Fig. 14]; horizontal shoots lacking winter bud constrictions [Fig. 14]; plants primarily of hydric habitats
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    Lycopodiella

    2a. Sporophylls green, superficially similar to the trophophylls of the upright shoots, arranged in 10 or more vertical ranks, 2.9–9 mm long; strobilus stalks with abundant and imbricate trophophylls; trophophylls of the horizontal shoots monomorphic; plants deciduous, overwintering by a thickened tip of stem (i.e., turion)
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    Pseudolycopodiella

    2b. Sporophylls stramineous at maturity, clearly differentiated from the trophophylls 
of the upright shoots, arranged in 4–10 vertical ranks, 2.7–3.3 mm long; strobilus stalks 
with few and remote trophophylls; trophophylls of the horizontal shoots dimorphic, 
the lateral trophophylls markedly wider than the median trophophylls; plants evergreen
• See list of 4 genera in 1b
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  1b. Upright shoots branched, with winter bud constrictions, produced from subterranean or superficial horizontal shoots; horizontal shoots with winter bud constrictions (except Dendrolycopodium), these marked by a zone of small, congested trophophylls; plants primarily of mesic to xeric habitats
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    Diphasiastrum

    3a. Branches 1–4.4 mm wide inclusive of the trophophylls, flat to quadrangular, with 
4 ranks of trophophylls (terete and with 5 ranks of trophophylls in one species) [Fig. 11]; branching of strobilus stalks, when present, dichotomous
  • See list of 3 genera in 3b
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    3b. Branches 5–12 mm wide, terete (somewhat compressed in D. obscurum), with 6 or more ranks of trophophylls; branching of strobilus stalks, when present, pseudomonopodial (i.e., falsely appearing to have a main axis from which branches arise)
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      Lycopodium

      4a. Strobili borne on stalks; trophophylls of the upright shoot branches arranged 
in alternating pseudowhorls of 6–10, tipped with a colorless hair 1.5–4 mm long
    • See list of 2 genera in 4b
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      4b. Strobili sessile; trophophylls of the upright shoot branches arranged in alternating pseudowhorls of 3–5, merely pointed or with a minute, but firm, spine-like tip
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        Dendrolycopodium

        5a. Upright shoots with an obvious main axis from which repeatedly forked branches arise (i.e., the shoots dendroid), bearing trophophylls that are merely pointed at the apex; horizontal shoots subterranean, lacking winter bud constrictions
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        Spinulum

        5b. Upright shoots with 1–4 subdichotomous branches (i.e., the shoots not dendroid and the main axis usually obscure), bearing trophophylls with a minute, but firm, spinule 0.4–1 mm long at the apex; horizontal shoots at or near the surface, with winter bud constrictions

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