Lycopodiaceae
Club-moss family.
Lycopodiaceae, club-moss family.
Vegetative morphology. Plants perennial herbs; (1–)2–14 cm high; caespitose, or not caespitose; low, moss-like, and evergreen, in tufts, or with long ground-level stems. Roots pallid-brown. Ground-level or under-ground stems horizontal, or not developed horizontally or vertically; rhizomatous, or stoloniferous (or not applicable); elongate (when present); 0.5–3 mm wide. Scales absent. Aerial stems erect; circular or oval in cross-section, or squarish; with 0 ridges, or 4 ridges. Leaves distributed along the stems; alternate (that contrasts with the Equisetaceae); evergreen. Petioles absent. Leaf blade bases truncate, or acute. Blades 0.2–3.5 mm long. Blades appressed to the stem; straight, or somewhat curled; linear, or elliptic, or triangular; with inconspicuous veins.
Reproductive morphology. Plants with sporangia, or with gemmae. Sporangia in the axils of unmodified leaves (Huperzia), or in terminal cone-like structures.
Notes. The Lycopodiaceae s.l. are an ancient and probably monophyletic
family without close living relatives. The family has a virtually cosmopolitan
distribution. Estimates of the number of species range from approximately 200 to
more than 500 (Ǿllgaard, 1987). Porsild placed all the taxa found in the
eastern Canadian Arctic Archipelago in genus Lycopodium. Extensive
research since then has lead to several revised classifications of the family.
Ǿllgaard (1987) provided information on: branching patterns, cortex and
stelar anatomy, distribution of mucilage cavities, leaf differention, morphology
of sporophylls, sporangia, spores, gametophytes, chromosome numbers, and
phytochemistry to reach the revised classification of the Lycopodiaceae he
proposed.
Wagner (1992) discussed cytological problems in Lycopodium
s.l. pointing out that the most important distinction between members of the
family and seed plants has to do with fertilization. The gametes involved in
"selfing" in seed plants arise from two different recombinant products of
meiosis and, therefore, selfing does not often produce homozygous offspring. On
the other hand, members of the Lycopodiaceae and Equisetaceae have the capacity
to produce completely homozygous offspring since a gametophyte and its gametes
are produced from a single haploid spore. This is referred to as
intragametophytic selfing.
Wagner and Beitel (1992), provided a generic
classification of modern North American Lycopodiaceae based on 50 characters of
anatomy, chromosomes, spores and gametophytes and analysed the data gathered
using his ground-plan-divergence method of cladistics (Wagner 1980). Wagner and
Beitel (1992) justified segregating taxa previously treated as being in the
genus Lycopodium,finding that the groups they recognized as separate
genera have many distinguishing features with strong gaps that separate them
from each other. These features include monophylesis, uniquely derived states,
inability to hybridize, and a level of segregation consistent and comparable
with generic divisions in other Pteridophytes.
Wagner and Beitel (1992) were
aware of the work of Josef Holub and Benjamin Ǿllgaard and recognized that
both had made extensive contributions to the knowledge and understanding of the
family including providing two systems of classification (Holub, 1983 and
Ǿllgaard, 1987). All three authors provide extensive references to the
earlier work on the Lycopodiaceae. While Wagner and Beitel (1992) limited their
work to North American members of the family they were aware that the
classification they proposed was closer to the ranks proposed by Holub (1983). A
modified version of a key to the genera for the three genera recognized in the
eastern Canadian Arctic follows based on Wagner and Beitel (1992).
1a.
Sporophylls like other leaves, photosynthetic; plants
epiphytic or
terrestrial; roots running from the apex
through the cortex before emerging;
leaves lacking
mucilageastern Canadaals; rhizomes absent;
spores
foveolate-fossulate; chromosomes x = 67–68. Sub-family
Huperzioideae
Plants producing specialized lateral bulbils (gemmiphores and
gemmae);
gametophytes unbranched; spore angles truncate, spore sides
concave;
..................................................................
Genus Huperzia Bernh.
1b. Sporophylls more or less strongly modified,
unlike other leaves,
nonphotosynthetic at maturity; plants terrestrial or
semiaquatic; leaves with basal mucilageastern Canadaals; roots
emerging
immediately, scattered along the rhizomes; spores various
but not
foveolate-fossulate .............................................Subfamily
Lycopodioideae
2a. Shoots round-branched, the mature leaves monomorphic and
separate,
in 6–8 ranks; sporangial wall cells with invaginations and
evanginations;
gametophytes gray or brown, flat, button-like and convoluted
when
mature; chromosomes x = 34.......................Genus
Lycopodium L.
2b. Shoots flat-branched, the leaves mostly dimorphic
or trimorphic
and overlapping; sporangial wall cells smoothly sinuate;
gametophytes
orange pigmented, narrowly top-shaped, nonconvoluted;
chromosomes x = 23, flat-branched clubmosses......Genus
Diaphasiastrum Holub.
Illustrations. • Lycopodiaceae: club-mosses. Family has sporangia borne in cones or, as in this case, the axils of unspecialized leaves. • Lycopodiaceae: young cone. Left, young fertile stobilus, or cone-like organ, with yellow sporangia just visible in the axils of the lower sporophylls. Right, sterile stem that has longer leaves. • Lycopodiaceae: old cones. Cone-like strobili that has opened to reveal sporangia borne in the axils of the leaves.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).
