Forestry & Forest Sciences · Foundations · also Plant Biodiversity and Taxonomy, Forest Botany, Botany for Foresters
Plant morphology, anatomy and the classification systems used to name and identify forest plants, from gymnosperms to the major angiosperm families of tropical and temperate forests.
In the exams: Background to ICAR AIEEA-PG Group 09 (dendrology) and IFoS Forestry Paper II Section B (forest ecology and ethnobotany)
Forest botany is the botany a forester needs: how trees and other forest plants are built, how they grow in girth year after year, how their roots, stems, leaves, flowers, fruits and seeds are formed and described, and how they are named, classified, collected and identified. Plant systematics, or taxonomy, provides the framework of names and classifications that lets a forester in Dehradun, Nairobi and Vancouver talk about the same species without confusion, and the herbaria, floras, keys and databases that make identification reliable.
The subject is foundational. Dendrology, the identification of trees in the field, builds directly on plant morphology and on the characters of the major families. Wood anatomy and properties builds on the cell types and secondary growth described here. Silviculture, seed technology and tree improvement all depend on accurate identification and on knowing how flowers, fruits and seeds work. Ethnobotany, the study of how people use and know plants, rests on correct naming and on voucher specimens. Forest ecology and forest types use the same names to describe communities and their distribution.
This manual covers the plant cell and tissues and secondary growth; the morphology of plant organs; the principles of the International Code of Nomenclature for algae, fungi, and plants; the classification systems of Bentham and Hooker, Engler and the Angiosperm Phylogeny Group; the main gymnosperm families of forests; the major angiosperm forest families; herbarium technique; floras, keys and databases; and the concepts and methods of ethnobotany. The subject is background to ICAR's AIEEA-PG forestry paper and to the ecology and ethnobotany section of the UPSC Indian Forest Service Forestry optional, and is examined directly in university courses worldwide.
The plant cell is enclosed by a cell wall outside the plasma membrane. The wall is made of cellulose microfibrils embedded in a matrix of hemicelluloses and pectins. Adjacent cells are cemented by the middle lamella, rich in pectin. Growing cells have a thin primary wall; many cells, once they stop growing, lay down a thicker secondary wall inside it, in layers often called S1, S2 and S3, and impregnate it with lignin, which makes the wall rigid, strong and resistant to decay. Wood is mostly secondary walls of dead cells, which is why its properties depend on the arrangement of cellulose, hemicelluloses and lignin, described in wood anatomy and properties. Inside the cell, the protoplast contains the nucleus, plastids including chloroplasts, mitochondria, endoplasmic reticulum, Golgi bodies and a large central vacuole. Cells are connected by plasmodesmata through the walls, and in thick-walled cells by pits, thin areas of the wall that allow water to pass between cells.
Plant tissues are grouped as meristematic or permanent. Meristems are regions of dividing cells: apical meristems at the tips of shoots and roots produce primary growth in length; lateral meristems, the vascular cambium and the cork cambium (phellogen), produce secondary growth in girth; intercalary meristems at the base of internodes, as in grasses and bamboos, add length below the tip.
Simple permanent tissues consist of one cell type. Parenchyma has living, thin-walled cells that store food, carry out photosynthesis and heal wounds; collenchyma has living cells with unevenly thickened walls that support young stems and leaves; sclerenchyma has dead cells with thick, lignified walls, either long fibres or short, irregular sclereids (stone cells, as in the grit of pears). Complex tissues consist of several cell types. Xylem conducts water and minerals and provides support; it contains tracheary elements (tracheids, and in most angiosperms also vessel elements joined end to end into vessels), fibres and xylem parenchyma. Phloem conducts sugars; in angiosperms it contains sieve-tube elements with companion cells, while gymnosperms have sieve cells with albuminous (Strasburger) cells, together with phloem fibres and parenchyma. The epidermis covers primary organs and bears stomata and hairs.
In gymnosperms and woody dicotyledons, the vascular cambium forms a continuous cylinder between xylem and phloem. Its fusiform initials, long and pointed, produce the axial cells of wood and inner bark, and its ray initials, short and squarish, produce the rays that run radially. Periclinal divisions of the cambium add secondary xylem (wood) towards the inside and secondary phloem towards the outside; far more xylem than phloem is produced. In seasonal climates the cambium is active in the growing season and dormant in the cold or dry season, and the wood formed early in the season (earlywood) differs in density and cell size from that formed later (latewood), producing visible growth rings, usually annual. As the tree ages, inner wood often stops conducting, its parenchyma dies and extractives are deposited, forming heartwood, while the outer, living, conducting wood is sapwood.
As the stem thickens, the epidermis is replaced by periderm. The cork cambium (phellogen) produces cork (phellem) to the outside and phelloderm to the inside; cork cells are dead, suberised and protective, and lenticels allow gas exchange. Bark, in the forester's sense, is everything outside the vascular cambium: secondary phloem (inner bark) and periderm (outer bark), with successive periderms forming rhytidome in many species. Monocotyledons such as palms and bamboos lack a vascular cambium and do not form wood by true secondary growth; palms reach their trunk diameter by establishment growth before the stem elongates, and bamboo culms reach full diameter as they emerge from the ground.
The root system anchors the plant and absorbs water and nutrients. A tap root system has a main root from the radicle with laterals, typical of dicotyledons and gymnosperms grown from seed; a fibrous or adventitious system arises from the stem base, typical of monocotyledons. Forest trees show special roots: buttress roots, plank-like flanges at the base of many tropical rain forest trees; stilt or prop roots, arching from the trunk, as in Rhizophora; pneumatophores, upward-growing breathing roots in mangroves such as Avicennia; aerial roots that become pillar-like props in banyan (Ficus benghalensis); root nodules with nitrogen-fixing bacteria in legumes and actinorhizal trees; and mycorrhizas, root-fungus associations. Root suckers arise from roots of species such as poplars and Dalbergia sissoo.
The stem bears nodes, where leaves and buds arise, separated by internodes. Buds may be terminal or axillary, and are protected by bud scales in many temperate trees. Stems are modified as thorns (sharp modified branches, as in Citrus and Bougainvillea), as cladodes or phylloclades (flattened green stems doing the work of leaves, as in Opuntia and Ruscus), and as tendrils in some climbers. Casuarina has green, jointed, needle-like branchlets bearing whorls of tiny scale leaves at each joint, so that the branchlets photosynthesise. Prickles, such as those on roses and on the trunk of Bombax ceiba, are outgrowths of the epidermis and cortex, not modified stems.
A leaf has a blade (lamina), often a stalk (petiole), and in many species a pair of stipules at the base. Leaves are simple, with one blade, or compound, with the blade divided into leaflets: pinnately compound with leaflets along a central axis (rachis), as in neem and mahogany; bipinnately compound, with leaflets on secondary axes, as in many acacias, Albizia and Leucaena; palmately compound, with leaflets radiating from one point, as in Bombax; or trifoliate, as in Butea. Leaf arrangement (phyllotaxy) is alternate (spiral), opposite or whorled; it is one of the most useful identification characters. Venation is reticulate (net-like) in most dicotyledons and parallel in most monocotyledons. Margins may be entire, toothed (serrate, dentate) or lobed; apices and bases have many shapes with standard terms. Many Australian acacias, such as Acacia auriculiformis and A. mangium, bear phyllodes, flattened leaf stalks that replace the compound blade in mature plants. Pellucid dots, translucent oil glands visible against light, mark families such as Myrtaceae and Rutaceae.
A typical flower has four whorls on a receptacle: the calyx of sepals, the corolla of petals, the androecium of stamens (each a filament and anther) and the gynoecium of carpels, each with an ovary, style and stigma. Flowers are bisexual or unisexual, regular (actinomorphic) or irregular (zygomorphic), with free or fused parts. The ovary is superior when the other parts arise below it, and inferior when they arise above it, as in Myrtaceae. Floral formulae and diagrams summarise these features and are standard tools for family recognition. Inflorescences, the arrangement of flowers on the axis, include the raceme, spike, panicle, umbel, head (capitulum), cyme and catkin (ament), a hanging spike of small unisexual flowers typical of oaks, birches, poplars and willows.
Fruits develop from the ovary, sometimes with other parts. Simple dry dehiscent fruits split open: the legume (pod) of Fabaceae splits along two seams; the capsule of eucalypts and teak's relatives opens by valves; the follicle opens along one seam. Simple dry indehiscent fruits do not open: the nut, such as the acorn of oaks in its cup (cupule); the samara, a winged fruit, as in maples and ashes, and winged fruits of dipterocarps, whose wings are enlarged sepals; and the achene. Fleshy fruits include the drupe, with a stony endocarp, as in mango and teak, and the berry, fleshy throughout, as in guava. Aggregate fruits develop from many carpels of one flower; multiple fruits develop from a whole inflorescence, as in jackfruit (Artocarpus) and the fig (a syconium, an enclosed inflorescence).
A seed consists of the seed coat (testa), the embryo with its radicle, plumule and one or two cotyledons (or several in many conifers), and stored food either in the endosperm (albuminous seeds) or in the cotyledons (exalbuminous seeds). In epigeal germination, the cotyledons are carried above the ground, as in many legumes and pines; in hypogeal germination, they stay below ground, as in oaks and mango. Seed handling and dormancy are covered in tree seed technology.
A standard description of a tree for identification moves from the general to the particular: habit (tree, shrub, climber; evergreen or deciduous; height and crown shape); bark (colour, texture, thickness, blaze and any exudate); branchlets (hairiness, lenticels, spines); leaves (simple or compound, arrangement, stipules, petiole, shape, size, margin, apex, base, venation, surfaces and hairs, glands); inflorescence; flowers (sex, symmetry, number and fusion of parts, ovary position); fruit (type, size, dehiscence, colour); and seed. Using precise morphological terms makes descriptions comparable with floras and keys. Many tropical trees flower briefly or out of reach, so vegetative characters of bark, leaves and exudates become essential; their field use is the subject of dendrology.
Common names vary between languages and regions and may refer to different plants; sal, teak and deodar are clear in India but other names, such as 'cedar' or 'mahogany', are applied to unrelated trees in different countries. Scientific names give each taxon one internationally accepted name. Botanical names are governed by the International Code of Nomenclature for algae, fungi, and plants (ICN), which is revised after each International Botanical Congress; the Shenzhen Code of 2018 was followed by a revision at the Madrid congress of 2024. Cultivated plants such as clones and cultivars are named under a separate code, the International Code of Nomenclature for Cultivated Plants (ICNCP).
The ICN rests on six principles. Botanical nomenclature is independent of zoological and bacteriological nomenclature, so the same generic name may exist in plants and animals. The application of names is determined by nomenclatural types. Nomenclature is based on priority of publication: the correct name is the earliest validly published one, with exceptions allowed by conservation. Each taxon with a given circumscription, position and rank can have only one correct name. Scientific names are treated as Latin regardless of their origin. The rules are retroactive unless expressly limited.
The starting point for the nomenclature of most vascular plants is Linnaeus's Species Plantarum, published on 1 May 1753, which established the consistent use of binomial names. A species name is a binomial: the generic name, capitalised, followed by the specific epithet, in lower case, both italicised, as in Tectona grandis. The name is often followed by the author citation, the abbreviated name of the botanist who published it, such as L. for Linnaeus and L.f. for his son; Tectona grandis L.f. was described by the younger Linnaeus. When a species is moved to another genus, the original author is placed in brackets before the author of the new combination. Tautonyms, in which the generic name and specific epithet are identical, are not allowed in botany, though they are allowed in zoology.
The principal ranks, from highest to lowest, are kingdom, division (phylum), class, order, family, genus and species, with intermediate ranks such as subfamily, tribe, subgenus, section, subspecies, variety and form. Names above genus have standard endings: orders end in -ales, families in -aceae, subfamilies in -oideae and tribes in -eae. Eight families have long-used alternative names that are also permitted: Leguminosae (Fabaceae), Palmae (Arecaceae), Gramineae (Poaceae), Cruciferae (Brassicaceae), Compositae (Asteraceae), Guttiferae (Clusiaceae), Labiatae (Lamiaceae) and Umbelliferae (Apiaceae).
Each name is tied to a type, usually a herbarium specimen. The holotype is the single specimen designated by the author; isotypes are duplicates of the holotype; a lectotype is chosen later from the original material when no holotype was designated or it is lost; a neotype is chosen when all original material is lost; an epitype is designated to clarify an ambiguous type; syntypes are specimens cited when no holotype was designated; paratypes are other specimens cited with the holotype. For a name to be validly published, it must be effectively published in a printed or, since 2012, an online publication meeting the Code's rules, accompanied by a description or diagnosis in Latin or, since 2012, English, with the type indicated. Names replaced by others for the same taxon are synonyms; the basionym is the name on which a new combination is based. Name changes, such as the transfer of many Indian acacias to Vachellia and Senegalia, follow these rules and new phylogenetic knowledge, and foresters must learn to track them.
Foresters often meet name changes. Some result from nomenclatural rules, when an earlier valid name is found and takes priority or a name is shown to be illegitimate; others result from taxonomic changes, when new evidence shows that a genus is not monophyletic and its species are moved, as with the division of Acacia, or that two species are the same. Official documents such as forest acts, schedules of protected species and timber trade lists may lag behind, so it is good practice to give both the current accepted name and the widely used older name, for example Vachellia nilotica (syn. Acacia nilotica), and to state the database followed.
Early classifications were artificial, using one or a few convenient characters. Linnaeus's sexual system (1753) grouped plants by the number and arrangement of stamens and carpels; it was easy to use but grouped unrelated plants together. Natural systems that followed, by de Jussieu and de Candolle, grouped plants by overall similarity using many characters. Phylogenetic systems aim to reflect evolutionary relationships, and modern ones are based on DNA sequence data.
George Bentham and Joseph Dalton Hooker published Genera Plantarum in three volumes between 1862 and 1883, describing all the genera of seed plants known to them from specimens, largely at Kew. Their system is natural rather than phylogenetic, based on de Candolle's. It divides seed plants into three classes: Dicotyledons, Gymnosperms and Monocotyledons, with the gymnosperms placed between the two groups of angiosperms. Dicotyledons are divided into Polypetalae (free petals), Gamopetalae (fused petals) and Monochlamydeae (one or no perianth whorl), and further into series, cohorts (orders) and families. The system was practical, based on careful study of specimens, and was adopted by many herbaria in the British Commonwealth, including Kew and most Indian herbaria, and by floras such as Hooker's Flora of British India, which is why it remains familiar in South Asian teaching. Its weaknesses are the placement of gymnosperms between dicots and monocots and the grouping of unrelated families by single characters.
Adolf Engler and Karl Prantl's Die natürlichen Pflanzenfamilien (1887–1915) was the first major system to attempt a phylogenetic arrangement covering the whole plant kingdom. It placed gymnosperms before angiosperms and monocots before dicots, and treated plants with simple, unisexual flowers without petals, such as the catkin-bearing families (the Amentiferae, including oaks, birches, willows and poplars), as primitive among dicots. This view of flower evolution is now rejected; simple flowers are generally seen as reduced, not primitive. Engler's system was widely used in herbaria and floras in continental Europe and North America. Later systems by Hutchinson, Takhtajan, Cronquist (1981), Thorne and Dahlgren considered magnolia-like flowers primitive and refined the arrangement of orders and families.
The Angiosperm Phylogeny Group (APG) classification is based on phylogenetic analysis of DNA sequences together with other evidence. Its versions were published in 1998 (APG), 2003 (APG II), 2009 (APG III) and 2016 (APG IV). APG recognises only monophyletic groups, those containing an ancestor and all its descendants, and arranges orders into informal clades: the ANA grade of early-diverging lineages (Amborella, water lilies and Austrobaileyales), the magnoliids, the monocots, and the eudicots, which include the large rosid and asterid clades.
APG changed the placement of many forest families. Bombacaceae, Tiliaceae and Sterculiaceae have been merged into Malvaceae, so silk cotton (Bombax), lime (Tilia) and Sterculia are now Malvaceae. Teak (Tectona), Gmelina and Vitex, formerly in Verbenaceae, are now in Lamiaceae. Caesalpiniaceae, Mimosaceae and Papilionaceae are treated as one family, Fabaceae; the Legume Phylogeny Working Group in 2017 recognised six subfamilies, with the former mimosoids forming a clade within Caesalpinioideae. Dipterocarpaceae are placed in the order Malvales, Myrtaceae in Myrtales, Meliaceae in Sapindales and Fagaceae in Fagales. Many herbaria are rearranging their collections according to APG, and modern floras follow it, but older Indian floras and many exam syllabi still use Bentham and Hooker, so foresters need to know both.
Gymnosperms are seed plants whose ovules are borne exposed on the surface of cone scales or similar structures, not enclosed in an ovary; they produce seeds but not fruits in the strict sense. Living groups are the cycads, Ginkgo, the Gnetales and the conifers. Conifers are mostly evergreen trees with needle-like or scale-like leaves, wood made almost entirely of tracheids without vessels (non-porous wood), and pollen and seed cones usually on the same tree. They dominate boreal and many temperate and montane forests and supply much of the world's softwood timber, pulp and resin. Most are wind-pollinated. Many have resin canals in wood and leaves.
Pinaceae, the pine family, is the largest conifer family of the northern hemisphere and includes the most important timber conifers. Its members have needle leaves borne singly or in clusters, woody seed cones with spirally arranged scales each bearing two winged seeds, and resin. Pinus has needles in bundles (fascicles) of usually two, three or five, held in a sheath at the base; chir pine (P. roxburghii) and chilgoza (P. gerardiana) have needles in threes, and blue pine (P. wallichiana) in fives. Cedrus, including deodar (C. deodara), has needles in tufts on short shoots and erect, barrel-shaped cones that break up on the tree. Abies (firs), such as the West Himalayan silver fir (A. pindrow), have flat needles leaving round scars and erect cones that disintegrate on the tree. Picea (spruces), such as P. smithiana, have needles borne on peg-like projections and hanging cones that fall whole. Larix (larches) are deciduous, with tufted needles on short shoots. Tsuga (hemlocks) and Pseudotsuga (Douglas-fir, with distinctive three-pointed bracts protruding from the cone scales) complete the main genera.
Cupressaceae, the cypress family, now includes the former Taxodiaceae. Its members have scale-like or needle-like leaves, usually in opposite pairs or whorls of three in the cypress group, and small woody or berry-like cones. It includes Cupressus (cypresses, including the Himalayan Cupressus torulosa), Juniperus (junipers, whose fleshy, berry-like seed cones are used to flavour gin), Thuja, Chamaecyparis, Calocedrus, and the redwood group: Sequoia (coast redwood, the tallest living trees), Sequoiadendron (giant sequoia, the most massive), Taxodium (swamp cypress, with knee roots), Metasequoia (dawn redwood, deciduous, known as a fossil before living trees were found in China in the 1940s), Cryptomeria (Japanese cedar, planted in the Darjeeling hills and elsewhere) and Cunninghamia (Chinese fir, a major plantation species in China).
Araucariaceae is an ancient southern-hemisphere family with large cones and broad or awl-shaped leaves. It includes Araucaria (monkey puzzle, Norfolk Island pine, Paraná pine and hoop pine), Agathis (kauri, valued timber trees of New Zealand and Malesia) and Wollemia, the Wollemi pine discovered in Australia in 1994. Araucaria species are widely planted as ornamentals in India.
Podocarpaceae is another mainly southern-hemisphere and tropical montane family. Its seed is usually borne singly on a fleshy, often coloured receptacle or covered by a fleshy structure, attracting birds that disperse it. It includes Podocarpus, Nageia, Dacrydium and Afrocarpus. In South Asia, Nageia wallichiana (formerly placed in Podocarpus) occurs in evergreen forests of the North-East and the Western Ghats. Other conifer families include Taxaceae, the yews, whose seeds are surrounded by a fleshy red aril and whose bark and leaves are the source of the anticancer drug paclitaxel (taxol), first isolated from the Pacific yew; Himalayan yew (Taxus wallichiana) has been heavily exploited for this purpose.
The other living gymnosperm groups are small but botanically important. Cycads are palm-like plants with stout trunks and crowns of stiff pinnate leaves, bearing large cones on separate male and female plants; Cycas circinalis and other Cycas species occur in Indian forests, and many cycads are threatened and protected in trade. Ginkgo biloba, the maidenhair tree, is the only living species of an ancient lineage, a deciduous tree with fan-shaped leaves and fleshy, foul-smelling seeds on female trees; it survived in China and is widely planted. The Gnetales comprise three unusual genera: Gnetum, mostly climbers and small trees of tropical forests, including Indian species, with broad leaves that look like those of flowering plants; Ephedra, jointed shrubs of dry and cold regions, including the trans-Himalaya, and the source of ephedrine; and Welwitschia of the Namib desert. Gnetales have vessels in their wood, unlike other gymnosperms, which once led botanists to think they were close relatives of flowering plants, a view not supported by DNA evidence.
Fabaceae, the legume family, is the third-largest angiosperm family and among the most important in tropical forests. Its fruit is the legume, a pod usually splitting along two seams; most members have compound leaves with stipules, and many form root nodules with nitrogen-fixing rhizobia. Traditional treatments recognised three subfamilies or families: Caesalpinioideae, Mimosoideae (small regular flowers in heads or spikes with many conspicuous stamens) and Papilionoideae or Faboideae (butterfly-shaped flowers with a standard, wings and keel). Forest members include Dalbergia (sissoo and Indian rosewood, D. latifolia), Pterocarpus (red sanders, P. santalinus, and bijasal, P. marsupium), Hardwickia binata, Xylia xylocarpa, Tamarindus indica, Saraca asoca, Butea monosperma, Pongamia (Millettia pinnata), Albizia, Prosopis, Leucaena and the acacias. The old broad genus Acacia has been split: Australian species such as A. mangium and A. auriculiformis keep the name Acacia, while many African and Asian species have been moved, for example babul to Vachellia nilotica and khair to Senegalia catechu.
Dipterocarpaceae is a family of tropical trees, dominant in the lowland rain forests of South-East Asia and important in South Asia. Members have simple, alternate leaves with stipules, resin canals that yield resins (dammar), and fruits enclosed by persistent sepals, some of which enlarge into wings; the name means 'two-winged fruit'. Many species flower and fruit in mast years. Major genera are Shorea (including sal, S. robusta, and the meranti and lauan timbers of Malesia), Dipterocarpus, Hopea, Vateria (white dammar, V. indica, of the Western Ghats) and Dryobalanops (Borneo camphor). Dipterocarps produce much of the world's tropical hardwood timber.
Myrtaceae has simple, usually opposite or alternate, entire leaves dotted with aromatic oil glands, flowers with many stamens and an inferior ovary, and fruits that are capsules or berries. Eucalyptus, with several hundred species native mainly to Australia, is the most widely planted hardwood genus in the world; its flower buds are capped by an operculum formed from fused petals or sepals, which falls at flowering, and its fruits are woody capsules. Other genera include Corymbia (bloodwoods, such as the lemon-scented gum), Syzygium (jamun and many others), Melaleuca and Psidium (guava).
Lamiaceae (Labiatae), the mint family, is mainly herbaceous, with square stems, opposite leaves and aromatic oils, but under APG it includes important trees transferred from Verbenaceae: teak (Tectona grandis), with large rough leaves, small white flowers in large panicles and drupes enclosed in an inflated papery calyx; Gmelina arborea, a fast-growing timber tree; and Vitex.
Meliaceae, the mahogany family, has mostly pinnately compound, alternate leaves without stipules, and flowers whose stamens are fused into a tube. It contains some of the world's most valued timbers: the true mahoganies (Swietenia macrophylla and S. mahagoni of tropical America, and African mahoganies of the genus Khaya), Indian red cedar (Toona ciliata), Chukrasia, Cedrela, and neem (Azadirachta indica) and Melia, valued for timber, shade and natural insecticides.
Fagaceae, the beech family, includes oaks (Quercus), beeches (Fagus), chestnuts (Castanea) and the Asian Castanopsis and Lithocarpus. Members have simple, alternate leaves, male flowers in catkins, and nuts held in a cup or spiny husk (the cupule), such as the acorn. Fagaceae dominate many temperate forests of the northern hemisphere and the montane forests of the Himalaya, where ban, moru and kharsu oaks are important, and they form ectomycorrhizas.
Many other families supply forest trees. Combretaceae includes Terminalia (arjun, saja, the myrobalans) and Anogeissus. Malvaceae, in the APG sense, includes Bombax, Ceiba, Sterculia, Grewia and Tilia. Moraceae includes figs (Ficus) and Artocarpus (jackfruit), with milky latex and multiple fruits. Anacardiaceae includes mango and cashew. Rubiaceae includes Adina, Haldina and Mitragyna, recognised by opposite leaves with stipules between the petioles. Euphorbiaceae and Phyllanthaceae include rubber and many small trees. Salicaceae includes poplars and willows. Casuarinaceae includes Casuarina. Poaceae includes the bamboos, and Arecaceae the palms and rattans. These are treated further in dendrology.
A herbarium is a collection of preserved plant specimens, usually pressed and dried and mounted on sheets, arranged in a classification and maintained as a scientific reference. Herbaria document what plants grow where and when, provide the types on which names are based, allow identifications to be checked, support floras and monographs, and record changes in distribution over time. Each herbarium has a standard code listed in Index Herbariorum, the global directory: K for the Royal Botanic Gardens, Kew, CAL for the Central National Herbarium of the Botanical Survey of India at Howrah, and DD for the herbarium of the Forest Research Institute, Dehradun, which is especially rich in forest plants. Herbaria are often accompanied by carpological collections of fruits and seeds, spirit collections of fleshy material, xylaria (wood collections, discussed in wood anatomy and properties) and, increasingly, DNA banks.
A good specimen is representative, includes as many diagnostic parts as possible (leaves showing both surfaces and arrangement, flowers, fruits, and for trees a note or sample of bark), and fits the herbarium sheet when pressed. Several duplicates are usually collected so that copies can be sent to other herbaria. For trees, fertile branches are reached with pole pruners, by climbing, or from fallen material, and the collector notes features that are lost in drying: height, girth, bark, blaze, exudate, smell, flower colour and abundance. Every specimen receives a collector's number, and field notes record the date, locality with coordinates and elevation, habitat, associated species, and local names and uses where relevant. Collecting must follow the law: permits are needed in protected areas and often for collecting at all, rare species should not be over-collected, and access and benefit-sharing rules apply, especially when specimens or material leave the country.
Specimens are arranged in folded newsprint between blotters in a plant press, with corrugated cardboard or aluminium ventilators to let air pass, and dried over gentle heat or in a drier, the press being tightened as material shrinks. Thick or succulent parts may be sliced or treated with alcohol or briefly heated to kill cells and speed drying. Dried specimens are protected from insects, traditionally by poisoning with chemicals such as mercuric chloride, which is toxic and now avoided, and today mainly by deep-freezing and by keeping the herbarium cool, dry and clean.
Specimens are mounted on standard acid-free herbarium sheets, commonly about 42 by 29 centimetres, by strapping or gluing, with fragments such as loose seeds kept in small packets on the sheet. A label in the lower right corner records the scientific name, family, locality, coordinates, elevation, habitat, collector and number, date and notes. Sheets are accessioned, stamped with a unique number, placed in genus and species folders, and filed in cabinets according to a classification system, traditionally Bentham and Hooker in Indian herbaria and increasingly APG. Type specimens are stored separately with special care. Many herbaria are digitising their collections, making images and data available online.
A flora is an account of the plants of a defined area, with keys, descriptions, distributions and often illustrations. A manual is a more compact identification guide. A monograph is a comprehensive treatment of a single taxon, such as a genus or family, across its whole range. A revision is a less exhaustive treatment of a taxon, often regional. A checklist lists the taxa of an area, usually with synonyms and distributions but without keys or descriptions. Each serves a different purpose, and identification usually starts with a regional flora or manual and ends with a monograph or a comparison with herbarium specimens.
The classic flora of the region is J. D. Hooker's Flora of British India, published in seven volumes between 1872 and 1897, which still underpins much of South Asian taxonomy. The Botanical Survey of India is producing the Flora of India, a modern national flora appearing in volumes over many years, and state and district floras. Regional classics used by foresters include J. S. Gamble's Flora of the Presidency of Madras, H. Collett's Flora Simlensis, and forest floras such as D. Brandis's Indian Trees (1906), which describes the trees, shrubs and woody climbers of British India, and R. S. Troup's The Silviculture of Indian Trees (1921), which combines description with silviculture. Floras of neighbouring countries include the Flora of Pakistan, the Flora of Bhutan, the Flora of Nepal and the Flora of Bangladesh, and forest floras exist for many tropical regions worldwide. Older floras follow Bentham and Hooker's arrangement and older names, so names should be checked against current databases.
Online databases now support identification and nomenclature. The International Plant Names Index (IPNI) records the publication details of names of seed plants, ferns and lycophytes. Plants of the World Online (POWO), maintained by Kew, and World Flora Online (WFO), an international consortium project that succeeded The Plant List, provide accepted names, synonyms, distributions and descriptions. Tropicos, maintained by the Missouri Botanical Garden, holds names, specimens and literature. The Global Biodiversity Information Facility (GBIF) aggregates specimen and observation records worldwide. JSTOR Global Plants provides images of type specimens. Regional resources include eFlora projects and national biodiversity portals. Different databases may accept different names for the same species, especially after recent changes, so a forester should note which source was followed.
Keys allow a plant to be identified by a sequence of choices. Dichotomous keys, the commonest in floras, present pairs of contrasting statements (couplets), each leading to another couplet or to a name. In indented keys, the alternatives of each couplet are indented to the same level and set apart from other couplets; in bracketed keys, the two alternatives of each couplet are placed together and numbered, which saves space. Multi-access keys allow characters to be used in any order. The design and use of keys, and field identification characters of trees, are covered in detail in dendrology.
Ethnobotany studies the relationships between people and plants: how cultures name, classify, use, manage and value plants. It includes the study of folk taxonomies, the ways communities classify plants, which often recognise the same species as scientists for useful and conspicuous plants but group or split others differently; ethnomedicine and ethnopharmacology, the use of plants as medicines and the study of their active compounds; economic botany, the study of plant products in trade; and the management of plants and landscapes by communities, including protection in sacred groves and the cultivation of trees in home gardens. Forest ethnobotany is closely linked to non-timber forest products and to traditional ecological knowledge, discussed in forest ecology, and to rights over knowledge and resources, governed in India by the Biological Diversity Act and internationally by the Convention on Biological Diversity and its Nagoya Protocol.
Ethnobotanical research combines botanical and social science methods. Researchers first obtain the prior informed consent of communities and individuals and agree how information will be used and shared; the International Society of Ethnobiology adopted a code of ethics in 2006 that sets out these obligations. Data are collected by semi-structured interviews, participant observation, free listing (asking informants to list all plants used for a purpose), pile sorting and ranking exercises, walks in the forest with knowledgeable people, focus group discussions and market surveys. Every plant mentioned is linked to a voucher specimen, deposited in a herbarium, so that local names can be matched reliably to scientific names; without vouchers, ethnobotanical data cannot be checked. Local names, parts used, preparation, purpose and the identity and number of informants are recorded systematically.
Several indices summarise ethnobotanical data. The relative frequency of citation (RFC) of a species is the number of informants who mention it divided by the total number of informants; if 30 of 60 informants mention a plant, its RFC is 0.5. The use value (UV) is the total number of uses reported for the species divided by the number of informants. The fidelity level (FL) for a particular use is the number of informants citing the plant for that use divided by the number citing it for any use, times 100; if 18 of the 24 informants who mention a plant cite it for fever, its fidelity level for fever is 75 per cent. The informant consensus factor, described in forest ecology, measures agreement on plants used for a category of ailment. These indices help compare plants and communities and identify candidates for further study, but they depend on sampling and interview methods and should be interpreted with care.
Documentation of traditional knowledge serves conservation, community rights and the prevention of misappropriation. India's Traditional Knowledge Digital Library, set up by the Council of Scientific and Industrial Research and the Ministry of AYUSH from 2001, documents published traditional medicinal knowledge in a form patent examiners can search, to prevent patents being granted on it; People's Biodiversity Registers document local knowledge at village level. Publishing knowledge that communities wish to keep private can harm them, so documentation must follow their consent.
A student should be able to describe plant tissues and secondary growth, use morphological terms correctly for leaves, flowers, fruits and seeds, write scientific names correctly with author citations, explain the principles of the ICN and the differences between Bentham and Hooker, Engler and APG, recognise the main gymnosperm and angiosperm forest families by their characters, collect, press and mount a herbarium specimen with a complete label, use a flora and key, and carry out an ethical ethnobotanical interview with voucher specimens.
A forester five years into practice identifies trees correctly in working plans, inventories and timber sales, collects and labels specimens of unknown plants for identification at a herbarium, checks names against current databases when preparing reports, records local names and uses during community work, and maintains a divisional reference herbarium or photographic collection.
A senior forester or herbarium manager directs regional floristic surveys, manages institutional herbaria and xylaria, ensures that permits and benefit-sharing rules are followed, resolves naming changes in official lists, and supports biodiversity registers and the protection of traditional knowledge with communities.
A taxonomist or ethnobotanist with long experience revises genera and families of forest plants using morphology and DNA, describes new species, prepares floras and monographs, studies the evolution and biogeography of forest trees, and leads ethnobotanical research that combines rigorous methods with community rights. Such work keeps names stable and identification reliable for all other forestry disciplines.
This manual covers principles and the main forest families; it does not provide species descriptions, keys to genera or complete family accounts, which belong to floras and to dendrology. Wood structure is treated only at the level of tissues and secondary growth; detailed wood anatomy belongs to wood-anatomy-properties. The most recent changes to the ICN after the 2024 Madrid congress and ongoing generic changes in families such as Fabaceae are mentioned only in outline; current databases should be consulted. Ethnobotanical uses of particular plants are not listed, because they require species-by-species verification and raise questions of consent and benefit sharing.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions.
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