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Diphasiastrum

Diphasiastrum hybrids can be locally common, particularly in mixed-species populations. Some of the hybrid individuals show reduction in proportion of well-formed spores; unfortunately, so do some collections of orthospecies from the region. Of note is that one nothospecies in particular, D. ×‌sabinifolium, may be located without either parent present. Reference: Wilce (1965).

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D. sitchense
1a. Trophophylls of the lateral branches monomorphic, arranged in 5 ranks, adnate to the terete branches less than 50% of their length, with stomates on both surfaces; strobilus stalks absent (rarely up to 1 cm tall); strobili solitary; plants commonly shorter than 12 cm, compactly branched, without an evident main axis
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1b. Trophophylls of the lateral branches di- or trimorphic, arranged in 4 ranks, those of  the lateral ranks adnate to the flat or quadrangular branches more than 50% of their length, with stomates on the abaxial (i.e., lower) surface only; strobilus stalks 0.5–15 cm long;  strobili 1–4 per stalk; plants commonly taller than 12 cm, usually dendroid
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  D. tristachyum
  2a. Trophophylls of the lower rank 1–2 mm long, similar in length to the trophophylls of the upper rank; branches narrow, quadrangular, 1.2–2 mm wide, blue-green; horizontal shoots subterranean, frequently buried deeper than 5 cm
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  2b. Trophophylls of the lower rank 0.3–1 (–1.5) mm long, noticeably shorter than the trophophylls of the other ranks; branches wider, flat, 2–4.4 mm wide, green; horizontal shoots superficial, at the surface or immediately below the litter
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    D. complanatum
    3a. Lateral branches of upright shoots with winter bud constrictions [Fig. 11], somewhat irregular, more 3-dimensional and not planar; strobili mostly 10–25 mm tall, without sterile tips; strobilus stalks usually becoming stramineous prior to sporangia dehiscence, mostly 0.4–0.7 mm in diameter, the successive branches separate, appearing as distinct dichotomies
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    D. digitatum
    3b. Lateral branches of upright shoots without annual constrictions, with regular and planar aspect; strobili mostly 20–40 mm tall, often some with a slender, sterile tip; strobilus stalks remaining green until after sporangia dehiscence, mostly 0.6–1 mm in diameter, the successive branches in close proximity, the strobili often falsely appearing in a pseudowhorl of 4 [Fig. 12]

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Show photos of: Each photo represents one species in this genus.