Equisetum is the only living genus of the class Sphenopsida and is considered a living fossil among pteridophytes.
1️⃣ Systematic Position
Kingdom: Plantae
Division: Pteridophyta
Class: Sphenopsida
Order: Equisetales
Family: Equisetaceae
Genus: Equisetum
2️⃣ Habit & Habitat
Perennial, rhizomatous herb
Mostly terrestrial, some semi-aquatic
Grows in moist, marshy places, riverbanks
Found in temperate and tropical regions
3️⃣ Sporophyte Structure
(a) Root
True adventitious roots
Arise from underground rhizome
(b) Stem
Main photosynthetic organ
Jointed stem with clear nodes and internodes
Internodes are hollow; ridges and furrows present
Silica deposition in epidermis (stem feels rough)
Branches arise in whorls from nodes
(c) Leaves
Small, scale-like microphylls
Arranged in whorls at nodes
Leaves are fused at base forming a sheath
Non-photosynthetic
4️⃣ Internal Structure (Anatomy)
Stem Anatomy
Epidermis with silica
Cortex differentiated into:
Chlorenchyma (in ridges)
Sclerenchyma (beneath furrows)
Stele: Ectophloic siphonostele
Large central cavity (pith cavity)
Carinal canals (protoxylem cavities)
Vallecular canals (cortical air canals)
5️⃣ Reproduction
(a) Vegetative Reproduction
By fragmentation of rhizome
By tubers (in some species)
(b) Asexual Reproduction (Spores)
Plant is homosporous
Sporangia borne on sporangiophores
Sporangiophores arranged in compact strobilus (cone) at shoot tip
Spores are green and possess elaters
Elaters help in spore dispersal
(c) Sexual Reproduction
Spores germinate to form gametophyte (prothallus)
Prothallus:
Green, free-living
Usually unisexual (sometimes bisexual)
Antheridia produce multiflagellate sperms
6️⃣ Fertilization
Water is essential
Motile sperms fertilize egg
Zygote develops into sporophyte
7️⃣ Life Cycle
Shows alternation of generations
Dominant phase: Sporophyte
Gametophyte independent
8️⃣ Primitive & Advanced Characters
Primitive:
Homosporous
Strobilus formation
Living fossil nature
Advanced:
Well-developed vascular system
Jointed stem with nodes & internodes
Specialized spore dispersal (elaters)
9️⃣ Economic & Ecological Importance
Used as scouring rush (silica-rich stem)
Medicinal uses (diuretic)
Used in soil erosion control
