Systematic Position of Selaginella
Division: Lycophyta
Class: Ligulopsida
Order: Selaginellales
Family: Selaginellaceae
Genus: Selaginella
Species: S.kraussiana (very common), S.monospora, S.adunca, S.picta
Occurrence:
Habit: grows in moist and shady hill sides
Epiphytic: S.oregana
Xerophytic: S.lepidophylla
Plant body
Other features:
Division: Lycophyta
Class: Ligulopsida
Order: Selaginellales
Family: Selaginellaceae
Genus: Selaginella
Species: S.kraussiana (very common), S.monospora, S.adunca, S.picta
Occurrence:
Habit: grows in moist and shady hill sides
Epiphytic: S.oregana
Xerophytic: S.lepidophylla
Plant body
- The plant body is the sporophyte, differentiated into root stem and leaves
- Creeping or erect plant body
- Stem: dichotomously branched later become monopodial
- Leaves: small, simple, sessile, green, thin microphyllous leaves. Unbranched midrib
- Function: photosynthesis
- Roots: Adventitious roots, dichotomously branched arising from the stem
Other features:
- Heterosporous nature.
- Eusporangiate
- Life cycle: Heteromorphic alternation of generation
- Ligule and rhizophores present.
- Small tongue shaped outgrowth or appendage present at the base of each young leaf on its adaxial or upper side.
- At the bas of ligule, a sheath of elongated secretory cells are present called as glossopodium
- protective organ
- Secretory organ that keeps sporangium and young leaf wet
- It originates from the regions of dichotomy of the stem or points of branching.
- Fragmentation S.rupestris
- Tubers: S. chrysocaulos
- Resting buds: in aerial branches S. chrysocaulos
- Selaginella is heterosporous and Eusporangiate: It bears two kinds of spores; microspores and megaspores produced inside microspoarngium and megasporangium on microsprophylls and megasporophylls respectively.
- Spores are produced inside sporangia in the axils of sporophylls.
- Sporophylls are organized into cones or strobilus
- Strobilus consists of a central axis on which microsporophylls and megasporophylls are arranged.
- The location of microsporangia and megasporangia varies between species
- Dehiscence by vertical splitting from the upper end into two valves
- Microspore are small in size and produced in large numbers inside microsporangium
- Male gametophyte develops within the microspore wall and produces ~ 256 spirally coiled bi-flagellated antherozoids.
- Megaspores are large in size, 1-4 numbers
- Megaspores germinates within megasporangium forming female gemetophyte bearing archegonia.
- Water is essential for fertilization
- The young sporophyte remains attached to the megaspore for some time later falls to the ground and form roots and become independent
Tags:
Selaginella