Field Key To Clubmosses of Northeast North America

1D Leaves 4 ranked - * 2B Leaves all same length 3B Branches square in cross section; trowel shaped leaves; < 12 cm .... Di. alpinum 3A Branches flattened; leaves at base of strobili widely spaced .... Di. sabinifolium 2A Top and bottom leaves shorter than lateral leaves 4C 4(3) strobili; glaucous blue color; branches square in cross section .... Di. tristachyum 4B 2-4 strobili; very regularly fan-shaped branches .... Di. digitatum 4A 1-2 strobili; annular constrictions visible; irregular leaf pattern .... Di. complanatum 1C Leaves 5 ranked .... 1B Leaves 6 ranked - Dendrolycopodium 5B Lateral leaves form single horizontal plane; branches flattened .... De. dendroideum 5A Top and bottom leaves form single vertical plane 6B Bottom leaf rank much shorter than others .... De. obscurum 6A All leaf ranks same length .... De. hickeyi 1A Leaves more than 6 ranked or ranks indistinguishable (unranked) 7D Lacking strobili; sporangia in zones on upright stems; leafy gemmae branchlets present - Huperzia* 8B Leaves distinctly toothed, obovate; woodland .... H. lucidula 8A Leaves entire or weakly toothed 9B Apical leaves nearly the same size as basal; gemmae in single whorl at branch tips; boreal, cool, damp habitats .... H. selago 9A Apical leaves smaller than basal leaves 10C Gemmae in 1-3 whorls at branch tips; apical leaves 5-8 mm, basal 3-6 mm, leaves mostly narrowly lanceolate, parallel sided; sandstone substrate .... H. porophylla 10B Gemmae scattered along upright branches; apical leaves (2.5-3 mm) 1/2 of basal (4-6 mm); alpine & subalpine .... H. appressa 10A Gemmae in 2-3 whorls at branch tips; apical leaves (3.5-5.5 mm) 2/3 of basal (4.5-7 mm) .... H. miyoshiana 7C Strobili stalked; leaf tips with long hair tip - 11B Branches often with 2 or more strobili .... Lm. clavatum 11A Branches with single strobili (rarely 2, if so attached at same point) .... Lm. lagopus 7B Strobili leafy; upright shoots never branched; of bogs and wet places; horizontal stems leafy, attached to substrate surface and rooting at frequent intervals - Lycopodiella*, Pseudolycopodiella 12B Plants typically <10 cm .... La. inundata 12A Plants typically >10 cm 13C Upright stems with sparse widely spaced leaves; horizontal stems often subterranean .... P. caroliniana 13B Strobili barely wider than stem .... La. appressa 13A Stobili much wider than stem; horizontal stems arched .... La. alopecuroides 7A Strobili sessile; upright stems 1-2X branched - Spinulum 14B Strobili >1.5cm (to 4.5cm); leaves broadest at middle .... S. annotinum 14A Strobili <1.5cm; leaves broadest at base .... S. canadense

GENERA (number of species) Dendrolycopodium - Ground Pine (3) Diphasiastrum - Ground Cedar (5) Huperzia - Firmoss (5) Lycopodiella - Bog Clubmoss (3) Lycopodium - Staghorn Clubmoss (2) Pseudolycopodiella - False Bog Clubmoss (1) Spinulum - Bristly Clubmoss (2)

COMMON NAMES With the revision of this family in the 1990s and 2000s, several common names now refer to multiple species and even multiple genera. In addition, many of the species already had multiple or regional common names. The common names below seem to represent a logical flow that is used by many, but certainly not all, authorities. Dendrolycopodium dendroideum - Common Groundpine Dendrolycopodium hickeyi - Pennsylvania Groundpine Dendrolycopodium obscurum - Flattened Groundpine - Alpine Clubmoss Diphasiastrum complanatum - Northern Ground Cedar Diphasiastrum digitatum - Southern Ground Cedar Diphasiastrum sitchense - Sitka Clubmoss Diphasiastrum tristachyum - Blue Ground Cedar Diphasiastrum sabinifolium - Savinleaf Ground Cedar Huperzia appressa - Mountain Firmoss Huperzia lucidula - Shining Firmoss Huperzia miyoshiana - Pacific Firmoss Huperzia porophila - Rock Firmoss Huperzia selago - Northern Firmoss Lycopodiella alopecuroides - Foxtail Bog Clubmoss Lycopodiella appressa - Southern Bog Clubmoss Lycopodiella inundata - Northern Bog Clubmoss Lycopodium clavatum - Staghorn Clubmoss Lycopodium lagopus - One-Cone Clubmoss Pseudolycopodiella caroliniana - Slender Bog Clubmoss Spinulum annotinum - Bristly Clubmoss Spinulum canadense - Northern Bristly Clubmoss

*HYBRIDS Nearly all clubmosses seem to cross within genera. Clubmosses that have characteristics intermediate to those in the key could reasonably be considered hybrids. Several species are likely fertile hybrids. Other hybrids are likely to exist including back crosses of hybrids with a parent species, even when the parent species is absent from the region. True sterile hybrids can be recognized by abortive or polymorphic spores. Recognized hybrids are listed below. In addition clubmosses seem to readily form ecotypes with significant variations between those growing in shade versus sun or at elevation. Diphasiastrum ×habereri (digitatum × tristachyum) Diphasiastrum ×issleri (alpinum × tristachyum) Diphasiastrum sabinifolium (sitchense × tristachyum) Diphasiastrum ×verecundum (complanatum × digitatum) Diphasiastrum ×zeilleri (complanatum × tristachyum) Huperzia ×bartleyi (lucidula × porophila) Huperzia ×buttersii (lucidula × selago) Huperzia ×josephbeitelii (appressa × selago) Huperzia porophylla (lucidula × appressa) Huperzia ×protoporophylla (lucidula × appressa) Lycopodiella ×brucei (appressa × prostrata) Lycopodiella ×copelandii (appressa × alopecuroides) Lycopodiella margueritae (inundata x alopecuroides) Lycopodiella ×robusta (inundata x alopecuroides) Lycopodiella subappressa (inundata x appressa) Lycopodiella ×gilmanii (inundata x appressa)

Sincere thanks to Arthur Haines for his corrections and comments.

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