1️⃣ Systematic Position (Classification)
Kingdom: Plantae
Division: Phaeophyta (Brown algae)
Class: Phaeophyceae
Order: Fucales
Genus: Fucus
2️⃣ Habitat
Marine alga
Found attached to rocks along sea coasts
Common in cold temperate regions
Grows in intertidal zones (between high and low tide marks)
3️⃣ Thallus Organisation (External Morphology)
Large, multicellular brown alga
Thallus is flat, ribbon-like
Shows dichotomous branching
Thallus differentiated into:
(a) Holdfast
Discoid
Attaches alga to rock
(b) Frond
Flattened, leaf-like body
Possesses a prominent midrib
📌 Unlike Sargassum, stipe is not clearly distinct
4️⃣ Special Structures
🔹 Air Bladders (Pneumatocysts)
Paired, gas-filled sacs
Present on either side of midrib
Provide buoyancy to the thallus
5️⃣ Internal Structure (Anatomy)
Thallus shows tissue differentiation:
(a) Meristoderm
Outermost layer
Actively dividing cells
(b) Cortex
Photosynthetic region
Stores reserve food
(c) Medulla
Central region
Conducts materials
Made of elongated, thick-walled cells
6️⃣ Cell Structure
Cell wall: cellulose + algin
Pigments:
Chlorophyll a & c
Fucoxanthin
Reserve food:
Laminarin
Mannitol
7️⃣ Nutrition
Autotrophic
Photosynthesis in marine habitat
8️⃣ Reproduction in Fucus
🔹 A. Vegetative Reproduction
Rare
By fragmentation
🔹 B. Asexual Reproduction
Absent
No spores are formed
🔹 C. Sexual Reproduction
Type: Oogamy
Plants are usually dioecious
Reproductive Structures:
(a) Receptacles
Swollen, club-shaped terminal branches
Contain reproductive cavities
(b) Conceptacles
Flask-shaped cavities inside receptacles
Open by ostiole
(c) Male Sex Organ – Antheridium
Produces many biflagellate antherozoids
(d) Female Sex Organ – Oogonium
Produces eight eggs
➡️ Fertilization occurs externally in seawater
9️⃣ Life Cycle
Diplontic life cycle
Main thallus is diploid
Gametes are the only haploid stage
Zygote directly develops into diploid plant
📌 Important contrast with green algae
🔟 Economic Importance of Fucus
✔ Useful
Source of algin
Used in manure
Source of iodine
Used in pharmaceuticals
❌ Harmful
Overgrowth may disturb marine ecosystems
