The Lycopodiales of the British Isles (Diphasiastrum, Huperzia, Isoetes, Lycopodium, Selaginella)


L. Watson and M. J. Dallwitz

Character List

#1. <Common name:>/

#2. <Synonyms:>/


#3. Stems <elongation>/

1. elongated, with numerous small leaves/

2. short and tuberous, with sheathing leaves crowded in dense rosettes/

#4. Stems <carriage>/

1. suberect, and rooting <directly> at the base only/

2. creeping, and rooting directly at intervals along their length/

3. creeping, and rooting from characteristic, leafless, root-bearing branches (rhizophores)/

#5. Stems <length>/

cm long/

#6. Stems <manner of branching>/

1. overtly dichotomising vegetatively/

2. ostensibly monopodial vegetatively <owing to unequal development from the original dichotomies>/

#7. Stems <whether dorsiventral>/

1. dorsiventrally organized, with four ranks of leaves/

2. not dorsiventrally organized <implicit>/

#8. Stems <whether with flattened branches>/

1. with non-flattened branches/

2. with only slightly flattened branches/

3. with strongly flattened branches/

#9. Stems <presence of secondary thickening>/

1. with anomalous secondary thickening <via a cambium external to the primary phloem, producing small quantities of vascular tissue centripetally, and generating centrifugally large quantities of so-called prismatic tissue, comprising a mixture of xylem, phloem and parenchyma>/

2. without secondary thickening/

#10. The old leaf bases <in Isoetes, persistence>/

1. persistent on the stem, short and blackish, each with two long points/

2. not persistent/

#11. Leaves <whether ligulate>/

1. ligulate/

2. eligulate/

#12. Leaves <arrangement>/

1. 4-ranked on the branches/

2. not 4-ranked/

#13. <Foliage> leaves <heterophylly>/

1. of two kinds: those of the two ranks on the upper side of the stem appressed and directed towards the stem apex, and those of the two lower ranks larger and spreading laterally/

2. all alike and spirally arranged <implicit>/

#14. <Foliage> leaves <length>/

mm long/

#15. <Foliage> leaves <appressed or spreading>/

1. appressed/

2. spreading/

#16. Leaves <whether hair-pointed>/

1. with long, filiform hair-like tips/

2. not hair-pointed <implicit>/

#17. <Heterosporous or homosporous>/

1. homosporous <sporangia and spores all alike>/

2. heterosporous/

#18. Sporophylls <modified or leaflike>/

1. resembling the foliage leaves/

2. differing markedly from the foliage leaves/

#19. Sporophylls <arrangement>/

1. aggregated into well defined terminal cones/

2. in fertile zones tending to alternate with sterile zones along the stems, rather than in well defined terminal cones/

#20. Cones <carriage>/

1. sessile at the tips of the normal shoots/

2. on long, erect peduncles which bear distant, appressed, scale-like leaves/

#21. The sporangia/

1. basal and subsessile on the adaxial surfaces of the sporophylls, non-septate/

2. very large, transversely and longitudinally septate and embedded in the leaf bases/

Ecology and distribution

#22. The megaspores <of Isoetes, surface ornamentation>/

1. covered with short, blunt tubercles/

2. covered with long, fragile spines/

3. with a reticulate ornamentation, neither tuberculate nor spiny/

#23. <Terrestrial or aquatic:>/

1. terrestrial <implicit>/

2. aquatic/

#24. <Habitat elevation:>/

1. lowland/

2. upland/

3. montane/

#25. <Habitat when terrestrial:>/

1. bogs/

2. heaths/

3. sandy places/

4. rock ledges/


#26. <Distribution in the British Isles:>/


#27. <General comments:>/


#30. <Illustrations:>/

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2007 onwards. The Lycopodiales of the British Isles (Isoetes, Lycopodium, Selaginella). Version: 1st September 2009.’.