Spikemosses

Order Selaginellales

The spikemosses exist as a single genus, Selaginella, with about 700 living species. They are a creeping group of plants, growing on the floor of many tropical and subtropical forests, in wetlands, as well as rock outcrops in temperate and alpine regions. Some species grow as a rosette in seasonal dry habits. During the dry period, the plants curls inward on itself, becoming brown and nest-like in appearance. When moisture returns, the plants uncurls to the green, rosette form. These plants have been named "resurrection ferns" in the nursery trade.

Above: Stems and leaves of Selaginella sp.

Sporophyte (=spore-producing) phase

Vegetative features

Stems

Leaves

  • Lycophylls or microphylls, usually in a planated fashion along stem

  • Exhibit a scale-like ligule on microphylls and sporophylls

Roots

  • Most roots are mostly adventitious created at points of branching

  • A leafless axis is created from an angle meristem and grows toward the soil

    • This axis is called a rhizophore, and produces roots at the distal tip.

      • Rhizophores are also found in large, extinct members of the lycopods (Lepidodendrales)

    • This rhizophore axis does not have a root cap, and can develop into a leafy shoot

Reproductive features

Spore cases (sporangia)

Gametophyte (=gamete-bearing) phase

  • Small, but multicellular gametophytes

  • Mega- and micro-gametophytes are endosporic (not released from spore)

  • They are also heterotrophic and not photosynthetic

    • Supply of nutrients is limited to what is contained in the original spore.

    • Development in males is limited to the formation of an antheridium (sterile jacket) containing up to 32 sperm.

    • Female gametophyte is larger and creates archegonium and rhizoids

    • Sperm are released and swim to the female gametophyte for fertilization

https://upload.wikimedia.org/wikipedia/commons/d/dd/Selaginella_canaliculata.jpeg

Above: Branching systems of Selaginella

https://upload.wikimedia.org/wikipedia/commons/b/be/Selaginella_pilifera0.jpg

Above: Strobili of Selaginella

Classification

Embryophytes

└Tracheophytes

└Lycophytes

└Lycopsida

└Selaginellales

Diversity

  • 1 extant family (Selaginellaceae); 1 extant genus (Selaginella)

  • ~750 extant living species

Geologic Age

Above: The Resurrection fern, Selaginella lepidophylla, a rare pteridophyte that lives in deserts, and "opens" when rains come.

Additional Resources