Economic Botany, Ethnobotany & Phytogeography BBO5T10

Syllabus topics (RTMNU)

• Food: Rice and Wheat
• Fibre: Cotton and Jute
• Vegetable oil: Groundnut and Mustard
• Spices: Clove and Cardamom

Economic botany is the study of plants useful to human beings — for food, fibre, oil, spices, beverages, timber, medicines and industry. For each plant learn: botanical name, family, the useful part and its structure, chief chemicals and uses.

Food: Rice

Botanical name and family: Oryza sativa L., family Poaceae (Gramineae). India is the second largest producer after China; main states: West Bengal, Uttar Pradesh, Punjab; also eastern Vidarbha (Gondia, Bhandara — "rice bowl" of Maharashtra).

Morphology (useful part):

• Annual grass, 60–150 cm tall, with fibrous adventitious roots and hollow, jointed stem (culm).
• Leaves long, narrow, with leaf sheath, ligule and auricles.
• Inflorescence a loose terminal panicle of one-flowered spikelets; flower with lemma, palea, 2 lodicules, 6 stamens and a feathery bifid stigma.
• Fruit a caryopsis (grain) — fruit wall fused with seed coat; covered by husk (lemma and palea). Below the husk lies the bran layer (pericarp + aleurone) and the starchy endosperm with a small embryo.

Chemical constituents: Starch about 75–80% (amylose and amylopectin), protein about 7–8% (mainly oryzenin), fat about 2% (mostly in bran), minerals and vitamin B complex, especially thiamine (B₁) in the bran. Polishing removes bran and B₁; eating only polished rice can cause beriberi.

Utilization:

• Staple food of more than half of India; cooked rice, idli, dosa.
• Products: poha (flattened rice), murmura (puffed rice), parboiled rice (retains more vitamins).
• Rice bran oil (edible); bran as cattle and poultry feed.
• Straw for fodder, thatching, paper and mushroom beds; husk as fuel in rice mills and boilers.
• Rice starch in textiles and cosmetics; fermented drinks.

Food: Wheat

Botanical name and family: Triticum aestivum L. (bread wheat; hexaploid, 2n = 42), family Poaceae. Also T. durum (macaroni wheat). Main states: Uttar Pradesh, Punjab, Madhya Pradesh, Haryana. A rabi (winter) crop.

Morphology (useful part):

• Annual grass, 60–120 cm, with fibrous roots and hollow culm.
• Inflorescence a compound spike (ear); each spikelet has two glumes and 2–5 florets; awns may be present.
• Fruit a caryopsis with a groove (crease) on one side and a tuft of hairs (brush) at the tip; husk separates easily on threshing.
• Grain: bran (pericarp + aleurone), large starchy endosperm and embryo (germ).

Chemical constituents: Starch 60–70%, protein 8–15%, fat 1.5–2%, fibre, minerals (iron) and B vitamins. The special proteins gliadin and glutenin form gluten when flour is kneaded with water; gluten makes dough elastic and lets bread rise.

Utilization:

• Atta (whole-wheat flour) for chapati, roti; maida for bread, biscuits, cakes; suji/rava for upma and halwa; daliya.
• Durum wheat for pasta, macaroni, vermicelli.
• Wheat germ oil (rich in vitamin E).
• Straw (bhusa) as cattle fodder, packing and paper.

Fibre: Cotton

Botanical name and family: Gossypium spp., family Malvaceae. Four cultivated species: G. hirsutum (American upland), G. barbadense (Egyptian / Sea-island), G. arboreum and G. herbaceum (Asiatic, desi). Gujarat and Maharashtra (Vidarbha — "white gold") are major producers. Bt cotton dominates Indian fields.

Morphology (useful part):

• Shrub, 1–2 m, with palmately lobed leaves and large yellow/cream flowers with an epicalyx and monadelphous stamens.
• Fruit a loculicidal capsule called a boll; it bursts to expose seeds covered with white hairs.
• The fibre is a surface fibre — each is a single-celled epidermal hair of the seed coat. Long hairs = lint (spun into yarn); short hairs = fuzz/linters.
• Under the microscope a cotton fibre is flat and twisted (convolutions), which helps in spinning.

Chemical constituents: Almost pure cellulose (about 90–95%), with small amounts of wax, protein, pectin, ash and water. The seed contains about 15–20% oil (with toxic pigment gossypol, removed on refining).

Utilization:

• Textiles — the most important natural fibre; khadi, denim, bed-sheets.
• Surgical (absorbent) cotton, bandages.
• Linters for rayon, paper, explosives (nitrocellulose) and stuffing.
• Cottonseed oil for cooking and vanaspati; oil cake as cattle feed.

Fibre: Jute

Botanical name and family: Corchorus capsularis (white jute) and C. olitorius (tossa jute), family Malvaceae (earlier Tiliaceae). India is the largest producer; West Bengal produces most of it. Called the "golden fibre".

Morphology (useful part):

• Annual herb, 2–4 m tall, slender, little branched stem.
• Leaves simple, serrate, with two tail-like projections at the base.
• Small yellow flowers; capsule round (C. capsularis) or long (C. olitorius).
• The fibre is a bast fibre — bundles of phloem fibres (sclerenchyma) in the stem bark. It is extracted by retting: bundles of stems are soaked in slow-moving water for 2–3 weeks; microbes rot the soft tissue; fibres are stripped, washed and dried.

Chemical constituents: A ligno-cellulosic fibre: cellulose about 60–65%, hemicellulose about 20%, lignin about 12–13%, plus fat, wax and pectin. Lignin makes it strong but it turns yellow and weak in sunlight.

Utilization:

• Gunny bags and sacks for packing food grains, sugar, cement.
• Hessian cloth, ropes, twine, carpet backing, mats.
• Geo-textiles for soil erosion control; eco-friendly shopping bags.
• Sticks as fuel and in particle board; young leaves of C. olitorius eaten as vegetable.

Vegetable Oil: Groundnut

Botanical name and family: Arachis hypogaea L., family Fabaceae. Native to South America. Gujarat is the leading state in India.

Morphology (useful part):

• Annual herb, erect or spreading; leaves pinnate with two pairs of leaflets.
• Yellow papilionaceous flowers. After fertilisation the stalk below the ovary (gynophore or "peg") grows down and pushes the ovary into the soil — this is called geocarpy.
• The pod (legume) ripens underground; it is indehiscent with 1–3 seeds; seeds have a thin red-brown seed coat and two large oily cotyledons.

Chemical constituents: Seeds contain 40–50% oil and 25–30% protein. Oil is rich in unsaturated fatty acids — oleic and linoleic acid — with some palmitic acid; also vitamin E and B vitamins.

Utilization:

• Cooking oil (moongphali tel); hydrogenated to make vanaspati.
• Seeds roasted, salted, in chikki and peanut butter.
• Oil cake — protein-rich cattle feed and manure.
• Shells as fuel and in hardboard; plants as fodder; the crop fixes nitrogen in soil.

Vegetable Oil: Mustard

Botanical name and family: Brassica juncea (Indian mustard, rai) and B. campestris (sarson, toria), family Brassicaceae (Cruciferae). Rajasthan is the leading state. Rabi crop.

Morphology (useful part):

• Annual herb, 1–1.5 m; lower leaves lyrate, upper leaves smaller.
• Bright yellow cruciform flowers with four petals and tetradynamous stamens (4 long + 2 short).
• Fruit a siliqua with a false septum (replum); many small round brown or yellow seeds.

Chemical constituents: Seeds contain about 35–45% oil. The oil has erucic acid (high in traditional varieties; low-erucic "canola"-type varieties are bred), oleic and linoleic acids. The sharp smell and taste come from allyl isothiocyanate, formed when the glucosinolate sinigrin is broken down by the enzyme myrosinase on crushing.

Utilization:

• Cooking oil in North and East India; pickles; oil for massage and hair.
• Seeds as a spice (tadka) and in mustard sauce.
• Leaves as vegetable (sarson ka saag).
• Oil cake as cattle feed and manure.

Spices: Clove

Botanical name and family: Syzygium aromaticum (L.) Merr. & Perry (syn. Eugenia caryophyllata), family Myrtaceae. Native to the Moluccas (Indonesia); in India grown in Kerala, Tamil Nadu (Nilgiris) and Karnataka.

Morphology (useful part):

• Evergreen tree, 10–12 m, with opposite, leathery, gland-dotted leaves.
• The spice is the dried unopened flower bud. Buds are picked when they turn from green to pink and dried in the sun till dark brown.
• A clove has a long stalk-like hypanthium (calyx tube) with four sepals and a round "head" of unopened petals.

Chemical constituents: Clove buds contain 15–20% essential (volatile) oil; the main compound is eugenol (about 70–90% of the oil), plus eugenol acetate and caryophyllene; also tannins.

Utilization:

• Spice in garam masala, biryani and sweets.
• Clove oil relieves toothache; used in dentistry, mouthwashes and toothpastes; antiseptic.
• Perfumes, soaps; eugenol is a raw material for vanillin.

Spices: Cardamom

Botanical name and family: Elettaria cardamomum (L.) Maton (small cardamom — "Queen of Spices"), family Zingiberaceae. Grows in the shade in the Western Ghats — Kerala (Idukki), Karnataka, Tamil Nadu. Large cardamom is Amomum subulatum (Sikkim).

Morphology (useful part):

• Perennial herb, 2–4 m, with an underground rhizome and leafy aerial shoots (pseudostem of leaf sheaths).
• Panicles arise from the base of the shoot and lie on the ground; flowers white with a striped labellum.
• Fruit a small, green, three-celled capsule with 15–20 black, aromatic seeds. Capsules are picked just before ripening and dried.

Chemical constituents: Seeds contain 2–8% essential oil, mainly 1,8-cineole and α-terpinyl acetate, which give the aroma; also starch, fixed oil and protein.

Utilization:

• Flavour for tea, sweets, kheer, biryani and coffee.
• Mouth freshener; digestive and carminative in Ayurveda.
• Oil used in perfumes and medicines.

Likely exam questions

1. (Long, 8 marks) Describe the morphology, chemical constituents and uses of rice and wheat.
2. (Long, 8 marks) Give the botanical name, family, morphology of the useful part, chemical constituents and uses of cotton and jute. Add a note on retting.
3. (Short, 4 marks) What is geocarpy? Explain with reference to groundnut.
4. (Short, 4 marks) Write the chemical constituents and uses of clove.
5. (Short, 4 marks) Why does mustard oil have a pungent smell? Give its uses.

Syllabus topics (RTMNU)

• Beverages: Tea and Coffee (Processing also expected)
• Rubber: Hevea brasiliensis (Processing also expected)
• General account of sources of firewood, timber and Bamboos

Beverages: Tea

Botanical name and family: Camellia sinensis (L.) Kuntze, family Theaceae. India is among the largest producers; Assam, West Bengal (Darjeeling), Tamil Nadu and Kerala (Nilgiri hills) are the main areas.

Morphology (useful part):

• Evergreen shrub or small tree; in gardens it is pruned to a bush about 1 m high ("plucking table").
• Leaves simple, alternate, serrate, leathery and shining; young leaves hairy.
• The useful part is the young shoot — "two leaves and a bud", plucked by hand every 7–10 days.
• Flowers white, fragrant; fruit a capsule.

Chemical constituents: Caffeine 2–4% (stimulant alkaloid), theophylline and theobromine in small amounts; polyphenols (catechins, tannins) up to 25–30% of dry leaf; during fermentation they are oxidised to theaflavins (brightness) and thearubigins (colour, body); the amino acid L-theanine; essential oils give aroma.

Utilization:

• Most popular beverage in India; mild stimulant.
• Green tea for antioxidants; tea extracts in medicines and cosmetics.
• Tea waste for caffeine extraction.

Processing of black tea (orthodox method):

1. Withering: fresh leaves are spread on racks or troughs with warm air for 12–18 hours; they lose about half their water and become soft.
2. Rolling: leaves are rolled in machines to break cells and twist them; the cell sap (with enzymes and polyphenols) comes out.
3. Fermentation (oxidation): rolled leaves are kept in a cool humid room for 2–3 hours; the enzyme polyphenol oxidase oxidises catechins; leaves turn copper-brown and develop flavour.
4. Drying (firing): hot air at about 90–100 °C stops fermentation and reduces moisture to about 3%; leaves turn black.
5. Sorting and grading: tea is sieved into grades (leaf, broken, fannings, dust) and packed.

In the CTC method (crush–tear–curl), withered leaves are passed through rollers that crush, tear and curl them into small granules — gives strong, quick-brewing tea. Green tea is not fermented: leaves are steamed or pan-fired first to destroy the enzyme. Oolong is semi-fermented.

Beverages: Coffee

Botanical name and family: Coffea arabica (Arabica) and C. canephora (Robusta), family Rubiaceae. Karnataka (Chikmagalur, Kodagu/Coorg) produces most of India's coffee, followed by Kerala and Tamil Nadu. Grown in shade on hill slopes.

Morphology (useful part):

• Evergreen shrub or small tree with opposite, shiny leaves and interpetiolar stipules.
• Flowers white, fragrant, in axillary clusters.
• Fruit a red fleshy drupe ("cherry") with two seeds lying face to face; each seed (bean) is covered by a parchment (endocarp) and a thin silver skin; the bean is mostly hard endosperm.

Chemical constituents: Caffeine (about 1–1.5% in Arabica, about 2–2.5% in Robusta), chlorogenic acids, the alkaloid trigonelline, sugars, fats and proteins. Roasting produces the brown colour and aroma (a complex of volatile compounds sometimes called caffeol).

Utilization:

• Beverage — filter coffee, instant coffee; stimulant.
• Caffeine for medicines and soft drinks.
• Pulp and husk as manure and cattle feed.

Processing:

1. Dry (natural) method: ripe cherries are dried in the sun for 2–3 weeks; dried fruit coat is removed by hulling — gives "cherry coffee".
2. Wet method: cherries are pulped to remove skin and pulp → beans fermented in tanks for 12–36 hours to remove the sticky mucilage → washed → dried to give "parchment coffee" → hulled to remove parchment → green coffee beans. Gives better quality ("plantation coffee").
3. Grading by size and quality.
4. Roasting at about 200–230 °C: beans swell, turn brown and develop aroma; then grinding.
5. Instant coffee: roasted ground coffee is extracted with hot water and the extract is spray-dried or freeze-dried into powder.

Rubber: Hevea brasiliensis

Botanical name and family: Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg., Para rubber, family Euphorbiaceae. Native to the Amazon basin (Brazil). In India Kerala produces most natural rubber; also Tripura and Karnataka.

Morphology (useful part):

• Tall tree, 20–30 m, with long-stalked trifoliate leaves.
• The bark contains latex vessels (articulated laticifers) in the secondary phloem, arranged in rings and running slightly spirally.
• Fruit a three-lobed capsule with oily seeds.

Chemical constituents: Latex is a milky emulsion: about 30–40% rubber (a polymer of isoprene, cis-1,4-polyisoprene, (C₅H₈)_n), about 55–60% water, with proteins, resins, sugars and mineral salts.

Utilization:

• Tyres and tubes (main use), footwear, belts, hoses.
• Gloves, balloons, rubber bands, medical items.
• Foam rubber for mattresses; seed oil for paints and soaps; old trees for rubber-wood furniture.

Processing:

1. Tapping: trees about 6–7 years old are tapped. A sloping half-spiral cut (from upper left to lower right, about 30°) is made in the bark early in the morning, when latex flow is highest. Latex flows along a spout into a collecting cup. A thin shaving is removed every 2–3 days.
2. Straining and dilution: latex is filtered to remove dirt and diluted with water.
3. Coagulation: dilute formic acid or acetic acid is added; rubber separates as a soft white mass (coagulum).
4. Sheeting: the coagulum is pressed between rollers into thin sheets.
5. Drying and smoking: sheets are dried in smoke houses to give Ribbed Smoked Sheets (RSS); washed and air-dried sheets give pale crepe rubber. Latex may also be concentrated (centrifuged) for gloves and balloons.
6. Vulcanisation: raw rubber becomes sticky in heat and brittle in cold. Heating with sulphur (discovered by Charles Goodyear, 1839) forms cross-links and makes rubber strong, elastic and durable.

General Account of Sources of Firewood, Timber and Bamboos

Firewood (fuelwood): wood burnt for cooking and heating; still the main fuel in many villages. Good firewood burns with high heat (calorific value), little smoke and little ash, dries quickly and grows fast. Sources: Acacia nilotica (babul), Prosopis juliflora (vilayati babul), Prosopis cineraria (khejri), Eucalyptus spp., Casuarina equisetifolia, Dalbergia sissoo (shisham), Azadirachta indica (neem), Leucaena leucocephala (subabul). Social forestry and energy plantations grow such fast-growing trees.

Timber: wood used for building, furniture, railway sleepers, boats and tools. Softwoods come from gymnosperms (no vessels); hardwoods from dicots (with vessels).

Bamboos: giant, woody, perennial grasses of family Poaceae (subfamily Bambusoideae) — the "poor man's timber" and "green gold". Stems (culms) are hollow with solid nodes; they grow very fast from underground rhizomes. Most species flower once after many years (often gregariously) and then die. Common species: Dendrocalamus strictus (male bamboo, common in Central India and Vidarbha forests), Bambusa bambos (thorny bamboo), Bambusa vulgaris, Melocanna baccifera (North-East). North-East India has the largest bamboo resources.

Uses of bamboo: house building, scaffolding, ladders, fencing; paper pulp (Ballarpur paper mills in Vidarbha); baskets, mats, furniture, handicrafts; agarbatti sticks; tender shoots as food; as fuel. The Indian Forest (Amendment) Act, 2017 removed bamboo grown outside forest areas from the definition of "tree", so farmers can cut and sell it more freely.

Likely exam questions

1. (Long, 8 marks) Describe the morphology, chemical constituents and processing of black tea.
2. (Long, 8 marks) Give an account of Hevea brasiliensis with reference to morphology, latex composition, tapping and processing of rubber.
3. (Short, 4 marks) Distinguish between the dry and wet methods of coffee processing.
4. (Short, 4 marks) Name any four timber-yielding plants with their families and uses.
5. (Short, 4 marks) Write a short note on the economic importance of bamboos.

Syllabus topics (RTMNU)

• Definition, Introduction, Branches and importance of Ethnobotany
• Ethnic societies of India: Gond, Korku, Santhal, Baiga and Bhil
• Ethnobotanically Important Plants (two plants each with reference to Family, parts used, tribal area)
• Vegetables: Cassia tora and Basella rubra
• Flower: Sesbania grandiflora and Madhuca longifolia
• Fruits: Diospyros melanoxylon and Aegle marmelos
• Seeds: Ocimum basilicum and Terminalia bellirica
• Roots and rhizomes: Chlorophytum tuberosum and Gloriosa superba

Ethnobotany: Definition, Introduction, Branches and Importance

Definition: Ethnobotany is the study of the direct relationship between plants and people — especially how tribal and traditional (ethnic) communities use plants for food, medicine, shelter, clothing, rituals and culture.

Introduction: The term ethnobotany was coined by the American botanist J.W. Harshberger in 1895. Tribal people live close to forests and have, over centuries, learnt which plants heal, which are edible and which are poisonous. This knowledge is passed orally from generation to generation and is being lost fast as forests shrink and lifestyles change. In India, Dr. S.K. Jain is called the father of Indian ethnobotany; the All India Co-ordinated Research Project on Ethnobiology (AICRPE) was started in 1982 to document tribal plant knowledge. India has more than 700 notified tribal communities (Scheduled Tribes).

Branches of ethnobotany:

1. Ethnomedicine / ethnopharmacology: plants used by tribes to treat diseases.
2. Ethno-nutrition (ethno-food): wild edible plants — leaves, fruits, tubers, flowers.
3. Ethno-veterinary botany: plants used to treat domestic animals.
4. Ethno-agriculture: traditional crops, seed-saving and farming methods.
5. Ethno-ecology: traditional knowledge of forests, sacred groves and conservation.
6. Ethno-taxonomy: local naming and classification of plants.
7. Magico-religious ethnobotany: plants in rituals, festivals and beliefs (e.g. sacred trees).
8. Palaeo-ethnobotany (archaeobotany): study of plant remains from ancient human sites.

Importance:

1. New drugs: leads for modern medicines — e.g. reserpine from Rauvolfia serpentina; tribal knowledge of Trichopus zeylanicus (arogyapacha) by the Kani tribe of Kerala led to the tonic "Jeevani".
2. Food security: wild edible plants can become new food crops.
3. Conservation: sacred groves and traditional practices protect biodiversity.
4. Documentation of fast-disappearing traditional knowledge (e.g. the Traditional Knowledge Digital Library, TKDL).
5. Protection of rights: helps prevent biopiracy (e.g. the neem and turmeric patent cases) and supports benefit-sharing under the Biological Diversity Act, 2002.
6. Livelihood: minor forest produce (tendu, mahua, musli) gives income to tribal families.

Ethnic Societies of India: Gond, Korku, Santhal, Baiga and Bhil

Ethnobotanically Important Plants

For each plant remember: family, part used, use and tribal area.

Likely exam questions

1. (Long, 8 marks) Define ethnobotany. Describe its branches and importance.
2. (Long, 8 marks) Describe the ethnic societies Gond, Korku, Santhal, Baiga and Bhil with reference to their area and use of plants.
3. (Short, 4 marks) Give the family, part used and ethnobotanical uses of Madhuca longifolia.
4. (Short, 4 marks) Write a note on Gloriosa superba as an ethnobotanical plant.
5. (Short, 4 marks) Give the family, part used and tribal use of Diospyros melanoxylon.

Syllabus topics (RTMNU)

• Principles of Phytogeography
• Distribution (Wides, Endemics and Discontinuous species)
• Theories (Landbridge and Continental Drift)
• Phytogeographical regions of India (Chatterjee, 1962): Name, distribution area and characteristic vegetation
• Climatic regions of India
• Vegetation types of India
• Grassland: Xerophilous, Mesophilous, Hydrophilous

Principles of Phytogeography

Phytogeography (plant geography) is the branch of botany that studies the distribution of plants on the earth's surface and the causes of this distribution. It has two parts: descriptive (floristic) phytogeography — where plants occur — and interpretive (ecological and historical) phytogeography — why they occur there.

Principles (based on Ronald Good, "The Geography of the Flowering Plants"):

1. Climate is the main controlling factor: temperature and rainfall decide which plants can grow where.
2. Edaphic (soil) factors are secondary but important for local distribution.
3. Each species has a range of tolerance to climate and soil; it can grow only within that range (Good's "theory of tolerance").
4. Plants migrate: by seeds, spores and vegetative parts carried by wind, water, animals and man.
5. Barriers (oceans, mountains, deserts) stop migration and isolate floras.
6. Past changes in climate (ice ages) shifted plant distributions.
7. Past changes in land and sea (continental drift, land bridges) explain many present distributions.
8. Evolution continuously produces new species, and extinction removes others.

Distribution: Wides, Endemics and Discontinuous Species

1. Wides (widespread / cosmopolitan species): plants that occur over a very large area, often in many continents. They have wide tolerance and good dispersal. Examples: Cynodon dactylon (doob grass), Chenopodium album, Portulaca oleracea, Taraxacum officinale; pan-tropical Tridax procumbens.

2. Endemics: species confined to a particular, usually small, area and found naturally nowhere else. Types: (a) Palaeo-endemics (relics) — old species that were once widespread but now survive in a small area, e.g. Ginkgo biloba (China); (b) Neo-endemics — young species that have not yet spread. Indian examples: Nepenthes khasiana (pitcher plant, Meghalaya), many Ceropegia species and Impatiens species of the Western Ghats. Western Ghats, the Himalaya and the North-East are endemic-rich biodiversity hotspots. Causes: isolation, narrow tolerance, poor dispersal, recent origin or loss of range.

3. Discontinuous distribution: a taxon occurs in two or more widely separated areas with a big gap between them. Examples: Magnolia and Liriodendron (tulip tree) in eastern Asia and eastern North America; Nothofagus in South America, New Zealand and Australia. Causes: continental drift, sinking of land bridges, extinction in the middle region (e.g. by glaciation), climatic change and long-distance dispersal.

Theories: Land Bridge and Continental Drift

Land bridge theory: It proposes that continents were once connected by narrow strips of land ("land bridges") over which plants and animals migrated; later these bridges sank under the sea, leaving discontinuous distributions. Example: the Bering land bridge joined Asia and North America during the ice ages. Criticism: there is no geological evidence for many of the proposed bridges across deep oceans.

Continental drift theory: Proposed by the German scientist Alfred Wegener (1912; book 1915). All continents were once joined in a single super-continent, Pangaea, surrounded by one ocean, Panthalassa. About 200 million years ago it broke into Laurasia (north: North America, Europe, Asia) and Gondwanaland (south: South America, Africa, India, Australia, Antarctica), separated by the Tethys Sea. These pieces slowly drifted to their present places; India drifted north and collided with Asia, raising the Himalaya.

Evidence: (1) jigsaw-like fit of coastlines of South America and Africa; (2) fossils of the seed fern Glossopteris in India, Africa, South America, Australia and Antarctica; (3) similar rocks and mountain chains on separated continents; (4) traces of ancient glaciation in now-tropical lands. Today the theory is explained by plate tectonics. It explains discontinuous distribution better than land bridges.

Phytogeographical Regions of India (Chatterjee, 1962)

D. Chatterjee (1962) divided India into nine phytogeographical (botanical) regions based on climate, topography and vegetation.

Climatic Regions of India

India has a tropical monsoon climate, but it varies greatly. Based on Köppen's scheme, the main climatic regions are:

1. Tropical monsoon / rain forest type (Amw): west coast (Konkan, Malabar) and parts of the North-East; heavy rain above 200 cm, short dry season.
2. Tropical savanna (Aw): most of the peninsular plateau; wet summer, dry winter.
3. Semi-arid steppe (BShw): rain-shadow Deccan (interior Maharashtra, Karnataka), parts of Gujarat, Haryana and Rajasthan; 40–75 cm rain.
4. Hot desert (BWhw): western Rajasthan (Thar); less than 25 cm rain, extreme temperatures.
5. Monsoon with dry winter (Cwg): the Gangetic plain and parts of Central India.
6. Cold humid winter with short summer (Dfc): Sikkim and Arunachal Pradesh.
7. Mountain / polar type (E/H): high Himalaya, Ladakh — cold, snow.

A simpler classification by rainfall: very high (>200 cm — Western Ghats, NE), high (100–200 cm — eastern and central India), low (50–100 cm — Deccan, upper Ganga plain) and very low (<50 cm — Rajasthan, Ladakh). Vidarbha gets roughly 100–150 cm (east wetter than west).

Vegetation Types of India

The standard classification is by Champion and Seth (1968) (16 forest type groups). The main types are:

1. Tropical wet evergreen forests: rain >250 cm; tall, dense, multi-storeyed — Western Ghats, NE, Andamans.
2. Tropical semi-evergreen forests: slightly drier fringes of the above.
3. Tropical moist deciduous forests: 100–200 cm rain; trees shed leaves in summer — teak, sal (eastern Maharashtra, MP, Odisha).
4. Tropical dry deciduous forests: 70–100 cm — teak, tendu, Anogeissus; large parts of the Deccan and Vidarbha.
5. Tropical thorn forests: <70 cm — Acacia, Prosopis, Euphorbia; Rajasthan, Gujarat.
6. Littoral and swamp (mangrove) forests: Sundarbans, Godavari–Krishna deltas, Andamans.
7. Subtropical pine forests (chir pine) and montane wet temperate / Himalayan moist and dry temperate forests (oak, deodar, fir, spruce).
8. Sub-alpine and alpine forests and scrub: birch, rhododendron, junipers, alpine meadows.

Grassland: Xerophilous, Mesophilous, Hydrophilous

Grasslands are plant communities dominated by grasses with few or no trees. In India most grasslands are secondary, kept by grazing and fire. They are grouped by moisture:

Likely exam questions

1. (Long, 8 marks) Describe the phytogeographical regions of India according to Chatterjee (1962) with their distribution area and characteristic vegetation.
2. (Long, 8 marks) Explain discontinuous distribution of plants. Discuss the land bridge and continental drift theories.
3. (Short, 4 marks) What are endemic plants? Give two examples from India.
4. (Short, 4 marks) State any four principles of phytogeography.
5. (Short, 4 marks) Distinguish between xerophilous and hydrophilous grasslands.