Selaginella is an advanced genus of Lycopsida and is very important from an evolutionary and exam point of view because it is a heterosporous pteridophyte.
1️⃣ Systematic Position
Kingdom: Plantae
Division: Pteridophyta
Class: Lycopsida
Order: Selaginellales
Family: Selaginellaceae
Genus: Selaginella
2️⃣ Habit & Habitat
Small, perennial herb
Mostly terrestrial, some epiphytic
Grows in moist, shady places
Some species are xerophytic (e.g., Selaginella lepidophylla – resurrection plant)
3️⃣ Sporophyte Structure
(a) Root
True roots present
Roots arise from special structures called rhizophores
Rhizophores are leafless, root-bearing organs
(b) Stem
Prostrate or erect
Dichotomous branching
Stem often dorsiventral
(c) Leaves
Small microphyllous leaves
Each leaf has a ligule at the base (ligule is a tongue-like outgrowth)
Leaves often dimorphic (two sizes)
Arrangement usually in four rows
4️⃣ Internal Structure (Anatomy)
Stem Anatomy
Epidermis with cuticle
Cortex parenchymatous
Stele: Protostele
Mostly actinostele
Xylem exarch
Trabeculae present (radial outgrowths connecting stele to cortex)
5️⃣ Reproduction
(a) Vegetative Reproduction
By fragmentation
(b) Asexual Reproduction (Heterospory)
Heterosporous plant
Two types of spores:
Microspores → male gametophyte
Megaspores → female gametophyte
Sporangia borne on sporophylls
Sporophylls arranged in strobili (cones)
(c) Sexual Reproduction
Gametophytes are endosporic (develop inside spores)
Male gametophyte:
Develops from microspore
Produces antheridia
Female gametophyte:
Develops from megaspore
Produces archegonia
Gametophytes are unisexual
6️⃣ Fertilization
Requires water
Multiflagellate sperms fertilize egg
Zygote develops into sporophyte within megaspore
7️⃣ Life Cycle Significance
Shows heteromorphic alternation of generations
Partial seed habit:
Heterospory
Endosporic gametophytes
Retention of megaspore
8️⃣ Economic & Ecological Importance
Ornamental plant
Selaginella lepidophylla used in drought studies
Important link between pteridophytes and seed plants
9️⃣ Comparison: Lycopodium vs Selaginella
Feature
Lycopodium
Selaginella
Spores
Homosporous
Heterosporous
Ligule
Absent
Present
Rhizophore
Absent
Present
Seed habit
Absent
Partial
