The Lycopodiales of the British Isles (Isoetes, Lycopodium, Selaginella)
Morphology. Stems elongated, with numerous small leaves; creeping, and rooting from characteristic, leafless, root-bearing branches (rhizophores); overtly dichotomising vegetatively; dorsiventrally organized, with four ranks of leaves (with two rows of leaves dorsally, and a row of larger leaves down each side); with strongly flattened branches; without secondary thickening. Leaves ligulate; 4-ranked on the branches; 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; about 1 mm long (on the upper side of the stem), or 2 mm long (on the sides); appressed and spreading.
Heterosporous. Sporophylls ovate, cuspidate, keeled; aggregated into well defined terminal cones. Cones sessile at the tips of the normal shoots (short, 4-sided). The sporangia basal and subsessile on the adaxial surfaces of the sporophylls, non-septate.
Ecology and distribution. Commonly grown in greenhouses, naturalized in Cornwall, Ireland and perhaps elsewhere.
Classification. Family Selaginellacae.
Ilustrations. • Habit. • Stem anatomy. • S. aff. krausiana, shoot and sporangia.
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. http://delta-intkey.com’.