A History of Agriculture in India v1.c10: Chapter 4. Vegetation

A History of Agriculture in India v1.c10

Language: English

v1.c10.s1 1. The Temperate Himalayan Region — 2 parts
v1.c10.s2 2. The Tropical Thorn Forests — 6 parts
v1.c10.s3 3. The Dry Deciduous Forests — 14 parts
v1.c10.s4 4. The Tropical Evergreen Rain Forests — 5 parts
v1.c10.s5 5. The Mangrove and Beach Forests — 10 parts

Chapter 4. Vegetation

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INDIA possesses a greater variety of vegetation than any other country. This is because of her geographical position (8° N to 37° N latitude and 63° E to 97.5° E longitude) as well as variations in altitude and climate. Immigration of plants from countries such as Malaya, China, Japan, Siberia, Arabia, Africa and Europe has also contributed to the variegated character of her flora. However, except at very high altitudes and in dry desert areas, the vegetation is essentially arboreal.

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A comparison of the Indian flora with the floras of the adjacent countries indicates that there is considerable Malayan element. The European element is represented in the western Himalayas by several genera and species. The African element comes next in the order of dominance. The Tibetan and Siberian types are confined to the Himalayas, and comprise mainly alpine herbs and shrubs. The Chinese flora is strongly represented throughout the temperate Himalayas by species of oaks and rhododendrons.

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The vegetation types described in this chapter concern largely the trees and shrubs under Phanerogams, together with a few Gymnosperms, which give character to the forests. It may be mentioned that within the areas under each type of vegetation, the occurrence and predominance of species are considerably influenced by physical factors, such as altitude, climate and soil.

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India can be divided into five regions on the basis of vegetation types. These are as below.

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1. The Temperate Himalayan Region: This region is further divided into two subregions, viz. the western Himalayas and the eastern Himalayas.

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2. The Tropical Thorn Forests: They occur in the Indus Plain Region comprising the Punjab, Haryana, Gujarat and Rajasthan west of the Aravalli Hills.

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3. The Dry Deciduous Forests: They occur in Rajasthan east of the Aravallis, southern Uttar Pradesh, Madhya Pradesh, central Maharashtra, a large part of Andhra Pradesh, Tamil Nadu and Karnataka.

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4. The Tropical Evergreen Rain Forests: They occur in the western face of the Western Ghats—the Konkan, Kanara, Kerala, Annamalais and the Nilgiris.

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5. The Mangrove and Beach Forests: They occur along the coastal region.

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These five regions and their vegetation types are described in the following account:

1. The Temperate Himalayan Region

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This region includes Assam (the Mishmi Hill tracts), Sikkim, northern Bengal, Kumaon and Garhwal, Himachal Pradesh, and Jammu and Kashmir. Rainfall is heavy in the outer ranges of the eastern portion. The northern portion is comparatively dry, though with more of winter rainfall, and the climate is almost of the Mediterranean type. There are thick forests of *sal* in the eastern portion.

i. The Western Himalayas

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In this region are included Kumaon, Garhwal, Himachal Pradesh, and Jammu and Kashmir. The western Himalayan region to the west of the Satluj differs from the eastern in its greater length, higher altitude, cooler and drier climate and far greater breadth of the mountainous masses. In the tarai area grow stately forests of *sal* (*Shorea robusta*) (Fig. 9). Above 1,220 metres the climate is temperate and humid and forests of *chir-pine*, *Pinus roxburghii*, are commonly found (Fig. 10). In the dry regions, e.g. Chini in Himachal Pradesh, *Pinus gerardiana* lends character to the landscape. Other common trees are the Indian horse-chestnut, maple and walnut.

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The *chir-pine* forests extend up to 1,980 metres and in their upper limit gradually get mixed up with white oak. The forest floor on the dry, south-facing slopes of the outer Himalayas are unusually open and grassy. On very exposed areas, *Euphorbia royleana* is common.

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From 1,830 metres upwards, *Quercus incana* becomes characteristic, associated with *Rhododendron arboreum* and *Lyonia ovalifolia* (*Andromeda elliptica*), with the straggling *Rosa brunonii* (*R. moschata*) covering them. Shrubs, such as *Indigofera gerardiana*, *Spiraea bella*, *Deutzia* sp., *Leycesteria formosa*, *Piptanthus nepalensis*, *Pyrus ursina*, *P. pashia*, *Rosa sericea*, *R. macrophylla*, *Viburnum foetens*, *Berberis*, *Ribes glaciale*, *Lonicera parviflora*, *Rubus lasiocarpus* and *Prunus padus* are common.

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At altitudes ranging from 2,130 to 3,050 metres, the characteristic trees are *Quercus semecarpifolia*, *Q. dilatata*, *Abies pindrow*, and *Cedrus deodara*. The typical oak forests consist of tall straight trees, laden with the lichen, *Usnea barbata*. The abies are also tall and stately, often reaching 61 metres in height. The principal associates of quercus-abies forests are *Arundinaria* sp. and *Taxus* sp. A few climbers, such as *Vitis semicordata*, *Clematis montana* and *Hedera nepalensis*, are also common. *Cedrus deodara* is the most stately tree in the Himalayas (Fig. 11). At about 2,740 to 3,050 metres *Pinus wallichiana*, *Picea smithiana* and *Cupressus torulosa* also occur in some localities. These forests usually grow on moist north-facing slopes, the sunny south-facing slopes being usually barren.

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*Rhododendron campanulatum*, with its pink and mauve flowers, occurs at about 3,050 metres. Interspersed with rhododendrons are *Taxus baccata*, *Betula utilis* and clumps of dwarf ringal bamboo, *Arundinaria falcata*. They mark the end of the tree zone at about 3,660 metres.

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The Alpine zone extends from 3,355 to 4,575 metres or sometimes even higher. Small bushes of *Juniperus recurva*, *Ephedra gerardiana*, *Rhododendron anthopogon* and *R. lepidotum* occur at 3,660 metres. Above 3,810 metres *Primula* occurs commonly, along with *Corydalis*, *Gagea* and *Aconitum lycotonum* (*A. laeve*). *Meconopsis aculeata*, the blue poppy, the pride of the Himalayan Alpine meadows, makes its appearance in July and August, along with the rare *Nomocharis*, which has purple-spotted yellow flowers. The cushion-like growth of *Arenaria festucoides* and some members of Caryophyllaceae and Crassulaceae are striking examples of xerophytic adaptations at high elevations. Gentians are represented by two species, and anemones by two, viz. *Anemone polyanthes* and *A. rupicola*. About eight species of *Potentilla* with all shades from deepest red to bright yellow, three species of *Primula*, light purple to deep, *Hackelia uncinata* (*Cynoglossum uncinatum*), *Androsace lanuginosa* and *Myosotis sylvaticus* (*M. pallens*) are also found in this zone.

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Most of the plants have thick hairy leaves and this characteristic is observed in the members of Saxifragaceae, Crassulaceae and Compositae. The cushion-like habit is seen in *Arenaria musciformis* and *Thylacospermum rupifragum* and in *Caragana pygmaea*. The carpet-like habit is to be met with in *Rhododendron anthopogon*, *Salix sclerophylla* and species of *Cotoneaster*.

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Another characteristic of Alpine vegetation in the trans-Himalayas is that the plants have brightly coloured flowers.

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ii. The Eastern Himalayas. In the Eastern Himalayas are included the regions of Sikkim, Bhutan, the Balipara Frontier Tract, and the outlying Patkai, Barail, Khasi and Garo ranges. The evergreen types of vegetation found in these areas are distinguishable into the following subzones.

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(a) The Assam and Brahmaputra and Surma Valleys. Along the eastern Himalayas and in the upper Brahmaputra and Surma Valleys, this forest type is represented by Meliaceae, Lauraceae, Myristicaceae, Magnoliaceae and others. The following species are typical of the lower slopes of the hills in upper Assam to the north of the Brahmaputra and the Naga Hills to the south of the river: *Dipterocarpus macrocarpus*, *D. gracilis*, *Artocarpus chaplasha*, *Shorea assamica*, *Cinnamomum cecidodaphne*, *Dysoxylum binectariferum*, *Altingia excelsa*, *Mesua ferrea*, *Pterygota alata*, *Michelia champaca*, *Amoora spectabilis*, *Toona ciliata* and *Kayea assamica*.

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Along the lower slopes of the Cachar, Khasi and Jaintia Hills and around the Surma Valley are found: *Dipterocarpus turbinatus*, *D. macrocarpus*, *Pterygota alata*, *Mesua ferrea* and *Bombax insigne* (*Salmalia insignis*). *Artocarpus chaplasha* and *Quercus* (oak) are also found in these belts.

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(b) The Northern Bengal Region. The northern Bengal region is characterized by *Schima-Bauhinia* in association with *Toona ciliata*, *Stereospermum personatum* (*S. tetragonum*), *Alilanthus grandis*, *Castanopsis indica*, *Tetrameles nudiflora*, *Michelia champaca* and *Gmelina arborea*. The undergrowth is composed of *Phoebe*, *Machilus*, *Amoora*, *Actinodaphne*, *Mesua* and *Polyalthia*.

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Bamboo thickets of *Bambusa arundinacea*, *Dendrocalamus hamiltonii*, *Oxytenanthera nigrociliata* and *Melocanna bambusoides* are also noticed in these forests.

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(c) The Eastern Sub-Himalayan Tract. This tract is humid, supporting a tropical flora up to an altitude of about 1,525 metres. The tropical evergreens are represented by species such as *Michelia champaca*, *Schima wallichii*, *Artocarpus chaplasha*, *Dillenia indica*, *Talauma hodgsonii*, *Aesculus assamica* (*A. punduana*), *Terminalia alata* (*T. tomentosa*), *T. myriocarpa*, *Bombax ceiba* (*Salmalia malabarica*), *Pterospermum acerifolium*, *Cinnamomum glanduliferum*, *Canarium sikkimense*, along with canes, climbers and an impenetrable undergrowth of evergreen shrubs.

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At lower elevations, *Magnolia* sp. and *Michelia champaca* are met with and at higher elevations *Castanopsis indica*, *Alnus nepalensis* and *Bucklandia populnea* are found.

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(i) The Sub-Himalayan Tract of Bengal and the adjoining regions of Assam, however, the typical wet evergreen is only locally recognizable in places. Sal forests have established themselves in much of the area, rendering the type as one of wet mixed forests. In these areas, the species associated with sal are: *Michelia champaca*, *Schima wallichii*, *Anogeissus latifolia*, *Terminalia alata* (*T. tomentosa*) and *Dendrocalamus hamiltonii*. In the Tista Valley of Sikkim, they are *Garuga pinnata*, *Terminalia bellirica*, *Schima wallichii*, *Lagerstroemia parviflora*, *Tetrameles nudiflora*, *Sterculia villosa*, *Toona ciliata*, *Bauhinia purpurea*, *Mallotus philippensis* and *Callicarpa arborea*.

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(ii) The laurel forest (approximately 1,830 to 2,135 metres) consists characteristically of *Machilus edulis*, *Beilschmiedia* spp., *Cinnamomum obtusifolium*, *Litsea* spp., *Alcimandra cathcarti* (*Michelia cathcartii*), *Magnolia campbellii*, *Engelhardtia spicata*, *Schima wallichii*, *Lithocarpus spicatus* (*Pasania spicata*), *Prunus nepalensis*, *Mallotus nepalensis*, *Betula alnoides*, *Acer laevigatum*, *A. campbellii*, *Eurya acuminata*, *Symplocos theaefolia*, *Castanopsis tribuloides* and members of Araliaceae.

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(iii) The buck-oak forest (approximately 2,135 to 2,440 metres) consists of *Quercus lamellosa*, *Acer campbellii*, *Castanopsis tribuloides* and *Michelia* sp.

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(iv) The high-altitude oak forest (approximately 2,440 to 2,745 metres) has *Lithocarpus pachyphyllus* (*Quercus pachyphylla*), intermixed with many of the buck-oak associates.

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(v) In the Alpine zone (above 3,655 metres) in the eastern Himalayas the prominent families are Compositae, Scrophulariaceae, Primulaceae, Saxifragaceae, Cruciferae, Caryophyllaceae, Ranunculaceae, Cyperaceae, Gramineae and Fumariaceae. The principal bushes are those of rhododendrons. The most widespread genera are *Pedicularis*, *Primula*, *Corydalis* and *Saxifraga*. The few trees, scattered at the lower limits of this zone, are birches and pyri. Junipers, and species of *Ephedra*, *Berberis*, *Lonicera*, *Caragana*, *Rosa*, *Cotoneaster*, *Spiraea* and dwarf willows occur. The flowering plant recorded at the highest altitude is *Festuca* at about 5,580 metres. In the drier valleys above 4,570 metres, several species of *Arenaria* occur, and form hard, hemispheric or globose, white, cushion-like structures. The most striking plants of this zone are *Meconopsis* sp., *Rheum nobile*, *Primula* spp., *Tanacetum gossypium*, *Saussurea obvallata*, *S. gossypiphora* and the odorous *Rhododendron anthopogon*.

2. The Tropical Thorn Forests

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These forests are characterized by a xerophytic flora of low and open formations, with many species adapted to xerophytic conditions. Thorny trees and plants are very common. Forests of this type are distributed over the Indus Plain region in southern Punjab, Haryana, Gujarat, Rajasthan, the Upper Gangetic Plains and in the Deccan Plateau.

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The Indus Plain Region. This region includes the Punjab, Haryana, Gujarat and Rajasthan to the west of the Aravalli Hills. With a few exceptions, all trees in this region are deciduous, and most of the herbs are desiccated and burnt in the hot season. The vegetation of this region is typically xerophytic. The principal indigenous trees are: *Tamarix aphylla* (*T. articulata*), *Sterculia urens*, *Grewia damine* (*G. salicifolia*), *Aegle marmelos*, *Moringa oleifera*, *Dalbergia sissoo*, *Butea monosperma*, *Prosopis cineraria* (*P. spicigera*), *Acacia nilotica* (*A. arabica*), *Salvadora persica*, *S. oleoides*, *Anogeissus pendula*, *Cordia dichotoma* (*C. myxa*), *Terminalia alata* (*T. tomentosa*), *Tecomella undulata*, *Ficus lacor* (*F. infectoria*) and *Morus indica*.

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Among the shrubs, the most conspicuous are the isolated clumps of the columnar, almost leafless *Euphorbia royleana* and *E. neriifolia*. Of special interest in this region are two species of cotton, *Gossypium stocksii* and *G. herbaceum* (*G. wightianum*). The other more or less prevalent shrubs and undershrubs in certain districts are: *Capparis decidua* (*C. aphylla*), *C. zeylanica* (*C. horrida*), *C. spinosa*, *Flacourtia ramontchi*, *Tamarix dioica*, *T. troupii* (*T. gallica*), *Grewia* sp., *Fagonia cretica* (*F. arabica*), *Rhamnus pentapomica* (*R. persica*), *R. virgata*, *Ziziphus nummularia*, *Z. jujuba* (*Z. vulgaris*), *Z. oenoplia*, *Dodonaea viscosa*, *Alhagi pseudalhagi* (*A. maurorum*), *Edwardsia mollis* (*Sophora mollis*), *Cassia auriculata*, *C. tora*, *C. obtusa* (*C. obovata*), *Mimosa rubicaulis*, *Pluchea lanceolata*, *Reptonia buxifolia*, *Carissa spinarum* (*C. diffusa*), *Rhazya stricta*, *Nerium indicum* (*N. odorum*), *Orthanthera viminea*, *Periploca aphylla*, *Calotropis procera*, *C. gigantea*, *Withania coagulans*, *Adhatoda vasica*, *Calligonum polygonoides*, *Pteropyrum oliveri*, *Salsola baryosma* (*S. foetida*) and species of *Kochia*. The fleshy *Suaeda* and *Salsola* grow on saline soils and *Calligonum polygonoides* on sandy soils.

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In the Thar Desert, the fleshy *Euphorbia neriifolia* is the most characteristic species. It is poisonous and is not eaten by cattle. This explains its widespread occurrence. Trees are also indicators of soil types to a large extent. *Salvadora persica* and *Prosopis cineraria* (*P. spicigera*) grow on loam.

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*Tamarix aphylla* (*T. articulata*) grows on saline soil, and, in areas where it grows, wells too have saline and bitter water. *Butea monosperma* grows on *usar* and *reh* lands impregnated with calcium bicarbonates on which no other trees can thrive.

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The trees found in the xerophytic forests of Rajasthan are those with reduced leaf surface or with fleshy leaves. Various species of *Acacia* and *Prosopis*, the commonest being *Acacia nilotica* (*A. arabica*) and *A. leucophloea*, are associated with *Prosopis cineraria* (*P. spicigera*) and the exotic *P. chilensis* (*P. juliflora*). *Acacia catechu* is found in considerable numbers in Kutch. In the southern Aravallis, *Anogeissus pendula* occurs in fairly homogeneous patches. Other typical species are *Salvadora oleoides*, *Tamarix aphylla* (*T. articulata*), *Ziziphus mauritiana* (*Z. jujuba*), *Grewia tenax* (*G. populifolia*) and *Ehretia laevis*. The undergrowth consists of *Capparis decidua* (*C. aphylla*), *C. spinosa*, *Asclepias* and *Calotropis*, with the fleshy *Suaeda* and *Salsola* growing on saline soils, and *Calligonum polygonoides* on sandy soils. *Euphorbia nivulia*, with a thorny stem, is also very characteristic at the foot of dry mountains.

3. The Dry Deciduous Forests

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These consist of low forests almost entirely of deciduous trees in all canopies. The following regions support a similar type of forests.

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The Upper Gangetic Plains. These plains include Rajasthan to the east of the Aravalli Hills, Bundelkhand, Malwa in Madhya Pradesh, and the Jhansi Division of western Uttar Pradesh. The indigenous vegetation of this subregion is that of a dry country. The trees in the dry season are leafless for the most part and the grasses and herbs get desiccated and burnt up in the hot season. The principal forest is that of Ajmer, flanking the Aravallis and other hills which bound the subregion on the west. The average rainfall is 635 millimetres. At the close of winter, temperature rises rapidly during March, and humidity goes down. High temperature shooting up to 45.6°C in the shade, and desiccating hot westerly winds from the rocky Aravalli Hills and the sandy deserts of Rajasthan, often accompanied with dust-storms in May and June, have produced a typical desert vegetation of xerophytes, with adaptations to guard against dry conditions and with devices to conserve moisture. The commonest trees are the leafless *Capparis decidua*, *Salvadora oleoides*, with tough leathery leaves, *Acacia nilotica* (*A. arabica*), *Prosopis cineraria* (*P. spicigera*), *Balanites aegyptiaca*, *Diospyros cordifolia*, *Ficus rumphii* and several species of *Tamarix*, with reduced scaly leaves. The wastelands between the villages are more or less barren, with only occasional patches of *Ziziphus nummularia* and *Salvadora persica*. Other trees more or less restricted to western India are *Moringa oleifera*, *Acacia senegal* and *Prosopis cineraria* (*P. spicigera*) accompanied with the common trees of the drier parts of India, especially *Butea monosperma*. Considerable [Figure: Fig. 12. A dry deciduous forest containing Boswellia serrata and Acacia catechu in Madhya Pradesh (Courtesy: Forest Research Institute)]

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Fig. 9. A forest of sal (Shorea robusta), Dehra Dun. Sal forests are found at the foothills of the Himalayas from Uttar Pradesh to Assam. They are also found in the forest belt comprising southern Bihar, western Orissa and eastern Madhya Pradesh (Courtesy: Forest Research Institute)

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Fig. 10. A young forest of Pinus roxburghii in the Siwaliks, Uttar Pradesh (Courtesy: Forest Research Institute)

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Fig. 11. A forest of Cedrus deodara near Simla, 2,134 metres above sea-leve'. Cedrus deodara is the most stately tree in the forests of the western Himalayas (Courtesy: Forest Research Institute)

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Fig. 13. A forest of teak (Tectona grandis) in Madhya Pradesh (Courtesy: Forest Research Institute)

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Fig. 14. A tropical wet evergreen forest in Kerala. Left to right: small Dipterocarpus bourdillonii, Vitex altissima, large Dipterocarpus, large Kingiodendron pinnatum and Polyalthia sp. Shendurney Coupe V, Shencottah Division, Kerala (Courtesy: Forest Research Institute)

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Fig. 15. The Nilgiri sholas and grassland, Ootacamund, Tamil Nadu. The shola forests are a living fossil community limited to the hollows, especially the heads of water-courses. Once destroyed, they do not regenerate (Courtesy: Forest Research Institute)

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[Figure: Fig. 16. Pure sundri forest (Heritiera fomes), Sunderbans, West Bengal, showing dense pneumatophore growth and buttressing of trees (Courtesy: Forest Research Institute)]

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areas of this subregion are occupied by the usar or reh land which, being impregnated with alkaline salts, are converted into swamps in the rainy season and into deserts in the dry season. *Salvadora persica* and *Butea monosperma* are the only trees that succeed on saline soils. The rocky areas are covered with hardy shrubs, e.g. *Anogeissus pendula*. Among the herbaceous vegetation we find such interesting xerophytes as *Leptadenia spartium* with erect, cylindrical, almost leafless branches, the spiny *Alhagi pseudalhagi* (*A. camelorum*), and the deep-rooted *Arnebia hispidissima*. In the shade of the prickly bushes of *Capparis sepiaria* grows the inconspicuous drought-resistant *Ceropegia bulbosa*, whose bulbous perennating stem is roasted and eaten by cowherds. Besides these, we find succulent herbs, such as *Portulaca oleracea* and *Salsola foetida*, which store up a large quantity of water in their leaves, and rosette plants with tough perennating rootstocks, such as *Boerhaavia diffusa* and *Euphorbia thymifolia*. Of the herbaceous plants, a few perennial-rooted grasses are the only ones which thrive.

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Central India. The commonest species are *Anogeissus acuminata*, *A. latifolia*, *Erythrina suberosa*, *Mangifera indica*, *Syzygium cumini*, *Albizzia odoratissima*, *Boswellia serrata*, *Lannea coromandelica*, *Sterculia urens*, *Terminalia bellirica*, *Ficus glomerata* and *F. religiosa*. The most conspicuous trees are *Boswellia serrata* and *Sterculia urens*. In the leafless condition, *Boswellia serrata*, with its peculiarly twisted branches and yellow stem, is a remarkable sight (Fig. 12). Its wood is used in manufacturing matchboxes, matchsticks and paper pulp. *Sterculia urens* yields gum katira, which is used in cosmetics. The commonest bamboo is *Dendrocalamus strictus*, which is also used for the manufacture of paper pulp. The following trees comprise the lower canopy of these forests: *Mallotus philippensis*, *Flacourtia ramontchi*, *Carissa spinarum*, *Emblica officinalis*, *Wrightia tomentosa*, *Bauhinia retusa*, *B. racemosa*, *Caesaria tomentosa*, *Butea monosperma*, *Holoptelea integrifolia* and *Dendrocalamus strictus*.

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The South-east Deccan. This region comprises the Eastern Ghats, Tamil Nadu, a large part of Andhra Pradesh and Karnataka. The vegetation is of a dry, thorny, stunted type. The commonest species are *Acacia planifrons*, *A. sundra*, *Mimusops* sp., *Azadirachta indica*, *Albizzia amara*, *Acacia latronum*, *Cailliea cinerea* (*Dichrostachya cinerea*), *Chloroxylon swietenia*, *Prosopis cineraria* (*P. spicigera*), *Bombax insigne* (*Salmalia insignis*) and *Osyris arborea*. The fleshy evergreen *Euphorbia* sp. also constitutes a characteristic feature of the vegetation. *Cassia auriculata* and *C. fistula* occur here and there, and the chief among the thorny shrubs are *Capparis* sp., *Carissa spinarum*, *Aristida adscensionis* and *Ziziphus* sp.

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Karnataka. The forests in the Karnataka region form an intermediate stage between the monsoon and xerophytic forests. The commonest forest tree is sandalwood. Other representatives are *Tectona grandis* and the associated *Terminalia* spp. and *Anogeissus latifolia*. Other species include *Dillenia pentagyna*, *Kydia calycina*, *Lagerstroemia lanceolata*, *Adina cordifolia*, *Madhuca indica* (*M. latifolia*), *Grewia asiatica*, *Pterocarpus marsupium*, *Lannea coromandelica*, *Bombax ceiba* (*Salmalia malabarica*), *Butea monosperma*, *Bridelia retusa*, *Diospyros melanoxylon* and *Emblica officinalis*. The chief bamboo is the well-known commercial variety, *Dendrocalamus strictus*.

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Grand forests of teak (*Tectona grandis*) grow in southern Madhya Pradesh (Fig. 13), Maharashtra, and the mountainous areas of Karnataka, Andhra Pradesh, Tamil Nadu and Kerala.

4. The Tropical Evergreen Rain Forests

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These forest types are developed in regions of very heavy rainfall and are characterized by the great variety and luxuriance of their vegetation, composed largely of dense mesophytic evergreens. Many trees attain great height and girth, and in these forests, three or four canopy layers or storeys are noticeable, dependent on the varying heights of the trees. Some species also develop characteristic buttressed stems at the base. Generally, the tree trunks are densely clothed with a thick felt of leafy Jungermanniales and mosses. The ground in these forests is usually covered with a dense growth of shrubby vegetation and ferns. Large woody climbers, tree-ferns, palms, bamboos and cane-breaks are also characteristics of these forests. Epiphytes are common.

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Typical evergreen forests are to be found along the West Coast of Peninsular India, particularly on the western face of the Western Ghats, the Konkan, Kanara, the Kerala, Annamalais and the Nilgiris. The greater part of it is hilly and mountainous, and the western face of the Western Ghats supports a dense vegetation of Malayan type, chiefly represented by members of Sterculiaceae, Tiliaceae, Anacardiaceae, Meliaceae, Myrtaceae, Melastomaceae, Vitaceae, Gesneraceae, Piperaceae, Zingiberaceae, Orchidaceae and Araceae. The species commonly met with in this region are: *Dipterocarpus indicus*, *Hopea parviflora*, *H. wightiana*, *Calophyllum elatum* (*C. tomentosum*), *Cullenia excelsa*, *Palaquium ellipticum*, *Dysoxylum malabaricum*, *Syzygium cumini*, *Actinodaphne angustifolia*, *Canthium dicoccum*, *Terminalia chebula*, *Carvia callosa*, *Toona ciliata*, *Vateria indica*, *Canarium strictum*, *Tetrameles nudiflora*, *Mesua ferrea*, *Mangifera indica*, *Pterygota alata*, *Acrocarpus fraxinifolius*, *Olea dioica* and *Xanthophyllum tomentosa* (*Pouteria tomentosa*).

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Forests of *Dipterocarpus* sp., *Kingiodendron pinnatum* and *Polyalthia* sp. provide timber to the people of Kerala (Fig. 14).

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Palms are represented by the species of *Arenga*, *Caryota* and *Corypha* with the cultivated *Areca catechu* and *Cocos nucifera* in places. Among undershrubs, *Strobilanthes* is important, and many species are noted for flowering at long intervals of 4, 6, 12 or even 15 years. Among herbaceous plants, *Impatiens* with about 60 species is conspicuous. In the mountain torrents in the Ghats, species of the family Podostemonaceae occur.

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The evergreen rain forests in the Western Ghats and those of Assam have much in common and also with the flora of Burma and Malaya. The cumulative effect of the Quaternary climatic and edaphic changes has reduced these forests to their present restricted distribution along the Malabar coast and in Assam. These forests now exist in the narrow belt of the country, more than 80 kilometres broad in the Western Ghats from Goa to Cape Comorin through Kanara and Coorg to the highlands of Kerala in the south and to parts of Tamil Nadu towards the east. In the drier parts, teak and sandalwood occur in these regions. The higher mountains are populated by species of *Ternstroemia*, *Microtropis*, *Michelia*, *Gordonia*, *Syzygium*, *Photinia*, *Rhododendron*, etc., along with the shrubs of Oleaceae, Rubiaceae, Rutaceae and various climbers and lianas. The patches of the forests in the ravines are called the *sholas*. Since the region is characterized by high humidity and abundant rainfall, it is in fact the pluvial flora that had advanced and retreated during the pluvial and interpluvial periods in Peninsular India and in Assam. Successive fluctuations must have occurred between the wet-evergreen and the dry-deciduous forests until their present distribution was attained. An interesting result of the Quaternary events and changes in climate is the reduction of the *shola* forests in the Nilgiris to the status of a living fossil community to which the present environment is so inimical that it has stopped regenerating itself (Fig. 15). Any injury to the *shola* forest is a permanent injury from which it never recovers.

5. The Mangrove and Beach Forests

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Throughout the tropics, particularly in the littoral regions in the estuaries of rivers, in creeks and lagoons of low-lying areas, is to be found a peculiar type of vegetation known as the mangrove vegetation or the mangrove swamp. In India and Pakistan, the mangrove forests are developed in suitable localities along the coastal region, from the Indus Delta in Sind southwards, along the West Coast of Peninsular India down to Kerala, and from the Sunderbans southwards along the East Coast of the Peninsula. They are also seen along the coast of the Andamans and the adjacent islands. The mangrove formations extend up rivers, sometimes for miles.

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The more common families represented in our typical mangrove forests are Rhizophoraceae, Meliaceae, Leguminosae, Combretaceae, Lythraceae, Rubiaceae, Myrsinaceae, Acanthaceae, Verbenaceae, Euphorbiaceae and Palmaceae.

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The following are some of the species met with in the mangrove forests of India and the Andamans: *Rhizophora mucronata*, *R. apiculata* (*R. conjugata*), *Ceriops tagal* (*C. candolleana*), *C. roxburghiana*, *Kandelia candel*, *Bruguiera conjugata* (*B. gymnorhiza*), *B. sexangula* (*B. eriopetala*), *B. cylindrica* (*B. caryophylloides*), *Xylocarpus granatum*, *Cynometra ramiflora*, *Aegialites rotundifolia*, *Xylocarpus molluccensis*, *Lumnitzera racemosa*, *L. littorea* (*L. coccinea*), *Sonneratia apetala*, *S. alba*, *S. caseolaris* (*S. acida*) *Scyphiphoya hydrophyllaceae*, *Aegiceras corniculatum*, *Acanthus ilicifolius*, *Avicennia officinalis*, *Excoecaria agallocha*, *Nipa fruticans* and *Phoenix paludosa*.

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As regards the distribution of the species in our mangrove forests, along the East and West Coasts of India and the Sunderbans and the Andamans, it is seen that whereas some species such as *Rhizophora mucronata*, *Bruguiera conjugata* (*B. gymnorhiza*), *Sonneratia caseolaris* (*S. acida*) and *Aegiceras corniculatum* are common to all these areas, a few others have rather a restricted distribution on the East Coast of Peninsular India and in regions east of it. Among this category may be mentioned *Xylocarpa molluccensis* *Scyphiphora hydrophyllaceae*, *Nipa fruticans* and *Phoenix paludosa*.

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One of the most extensively developed mangrove forests in India is in the Sunderbans in the Ganges Delta. In this forest belt, there are about 50 species of trees which may be conveniently classified into: (1) purely estuarial species, and (2) species common to other parts of India. Among the purely estuarial species are: *Hibiscus tiliaceus* (*H. tortuosus*), *Thespesia populnea*, *Brownlowia lanceolata*, *Amoora cucullata*, *Xylocarpus molluccensis*, *X. granatum*, *Bouea burmanica* (*B. oppositifolia*), *Erythrina variegata*, *Afzelia bijuga*, *Rhizophora apiculata* (*R. conjugata*), *R. mucronata*, *Ceriops roxburghiana*, *Kandelia candel*, *Bruguiera conjugata* (*B. gymnorhiza*), *B. parviflora*, *Lumnitzera racemosa*, *Barringtonia racemosa*, *Sonneratia apetala*, *S. caseolaris* (*S. acida*), *Aegialites rotundifolia*, *Aegiceras corniculatum*, *Cerbera odollam*, *Avicennia officinalis*, *A. alba*, *Excoecaria agallocha*, *Sapium indicum*, *Casuarina equisetifolia*, *Nipa fruticans* and *Phoenix paludosa*. To these may also be added *Hibiscus tiliaceous*, *Dalbergia spinosa*, *D. candenatensis* (*D. torta*), *Mucuna gigantea*, *Derrisinuata* and *D. trifoliata* (*D. uliginosa*), *Finlaysonia obovata*, *Sarcolobus globosus*, *Acanthus ilicifolius* and *A. volubilis*.

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Of the species common to inland Bengal, the following may be mentioned: *Kleinhovia hospita*, *Micromolum pubescens*, *Aegle marmelos*, *Ziziphus mauritiana* (*Z. jujuba*), *Lannea coromandelica*, *Cassia fistula*, *Pongamia pinnata*, *Acacia tomentosa*, *A. nilotica* (*A. arabica*), *Barringtonia acutangula*, *Ixora arborea* (*I. parviflora*), *Morinda bracteata*, *Diospyros montana*, *D. peregrina* (*D. malabarica*), *Cordia dichotoma* (*G. myxa*), *Dolichandrone spathacea* (*D. rheedii*), *Vitex trifolia*, *V. negundo*, *Drypetes assamica* (*Cyclostemon assamicus*), *Croton oblongifolius*, *Antidesma ghaesembilla*, *Trewia nudiflora*, *Streblus*, *Trema* and *Ficus*.

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The root-system of mangroves is characterized by special adaptations to their environments, which are often water-logged and poorly aerated. Some species as *Rhizophora* have a system of aerial stilt roots to support the trees; others, e.g. *Bruguiera*, send up peg-like projections from their roots; still others, e.g. *Heritiera*, *Lumnitzera* and *Kandelia*, produce aerial ‘knee roots’; and yet others, e.g. *Avicennia*, have pneumatophores or breathing roots. In the Sunderbans are found ‘pure sundri’ forest (*Heritiera minor*, *H. fomes*) with dense pneumatophore growth (Fig. 16).

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The members of Rhizophoraceae exhibit a peculiar phenomenon known as vivipary. Owing to this phenomenon, while the fruit is still attached to the parent tree, the embryo begins to grow, the hypocotyl protrudes, and the scedling hangs vertically from the fruit itself.

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Beach Forests. Before concluding this chapter, a brief mention may also be made of a narrow belt or strip of vegetation seen along the coast, and a little farther from the high-tide limits, known as the beach forests. In this belt, the trees are partly evergreen and partly deciduous. In places, *Casuarina equisetifolia* is cultivated extensively.

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Among the more common species may be mentioned: *Mimusops littoralis*, *Pongamia pinnata*, *Morinda citrifolia*, *Erythrina variegata*, *Calophyllum inophyllum*, *Terminalia catappa*, *Barringtonia asiatica* (*B. speciosa*), *Cordia subcordata*, *Thespesia populnea*, *Vigna marina* (*V. retusa*), *Mucuna gigantea*, *Colubrina asiatica*, *Calotropis gigantea* and *Pandanus odoratissimus* (*P. tectorius*).