18BZO14A-U5 Bentham and Hooker’s System of Classification The most important and the last of the natural systems of classification of seed plants was proposed by two British taxonomists George Bentham (1800-1884), a self trained botanist, and Joseph Dalton Hooker (1817-1911), the first director of the Royal Botanical Garden, Kew (England).They recorded precise description of most of the plants known at that time. Their monumental work which took about quarter of a century for completion was described in three volumes of Genera Plantarum, published in Latin during July 1862 and April 1883. Bentham and Hooker’s system of classification is still used and followed in several herbaria of the world. It is supposed to be the best system for the students to identify plants in the laboratory. Salient Features of Bentham and Hooker’s system: 1. It is a classification of only the “seed plants” or phanerogams. 2. They described 97,205 species of seed plants belonging to 7,569 genera of202 families starting from Ranunculaceae up to Gramineae. 3. They classified all the seed plants into 3 groups or classes i.e. Dicotyledons (165 families), gymnosperms (3 families) and monocotyledons (34 families). 4. They included disputed orders among Ordines Anomali which they could not place satisfactorily. 5. Monocotyledons were described after the dicotyledones. 6. The dicotyledons were divided into 3 Divisions (Polypetalae, Gamopetalae and Monochlamydeae) and 14 series. Each series again divided into cohorts (modern orders) and cohorts into orders (modern families). 7. The authors did not mention anything about the origin of the angiosperms. 8. Creation of the Disciflorae, a taxon not described by the earlier taxonomists. 9. Among the Monochlamydeae, major taxa, like the series, were divided on the basis of terrestrial and aquatic habits. 10. Polypetalae carries 82 families, 2610 genera & 31,874 species. Gamopetalae carries 45 families 2619 genera & 34,556 species. Monochlamydae includes 36 families, 801 genera & 11,784 species. Similarly Monocotyledons consist 34 families, 1495 genera and 18,576 species. Merits of Bentham and Hooker’s System: 1. Each plant has been described either from the actual specimen or preserved herbarium sheets so that the descriptions are detailed as well as quite accurate. 2. The system is highly practical and is useful to students of systematic botany for easy identification of species. 3. The flora describes geographical distribution of species and genera. 4. The generic descriptions are complete, accurate and based on direct observations. 5. Larger genera have been divided into sub genera, each with specific number of species. 6. Dicots begin with the order Ranales which are now universally considered as to be the most primitive angiosperms. 7. Placing of monocots after the dicot is again a natural one and according to evolutionary trends. 8. The placing of series disciflorae in between thalami florae and calyciflorae is quite natural. 9. The placing of gamopetalae after polypetalae is justified since union of petalsis considered to be an advanced feature over the free condition. Demerits of Bentham and Hooker’s System: 1. Keeping gymnosperms in between dicots and monocots is anomalous. 2. Subclass monochlamydeae is quite artificial. 3. Placing of monochlamydeae after gamopetalae does not seem to be natural. 4. Some of the closely related species are placed distantly while distant species are placed close to each other. 5. Certain families of monochlamydeae are closely related to families in polypetalae, e.g. Chenopodiaceae and Caryophyllaceae. 6. Advanced families, such as Orchiadaceae have been considered primitive in this system by placing them in the beginning. Placing of Orchidaceae in the beginning of monocotyledons is unnatural as it is one of the most advanced families of monocots. Similarly, Compositae (Asteraceae) has been placed near the beginning of gamopetalae which is quite unnatural. 7. Liliaceae and Amaryllidaceae were kept apart merely on the basis of characters of ovary though they are very closely related. 8. There were no phylogenetic considerations 1. Characters of Annonaceae 2. Distribution of Annonaceae 3. Economic Importance Characters of Annonaceae: Wood aromatic, leaves exstipulate, floral parts usually numerous, free spirally arranged; stamens with distinctive enlarged and flat connective; gynoecium multipistilate, apocarpous. A. Vegetative characters: Habit and habitat: Trees, shrubs or lianas. Artabotrys climbs by means of hooks. Oil ducts present in the bark, leaves and perianth leaves. Terrestrial and perennial. Evergreen, deciduous, cultivated as well as wild. Root: Tap, deep and extensively branched. Stem: Erect, branched, solid, woody, sometimes woody climbers. Leaves – Simple, entire, alternate, exstipulate, distichous, gland dotted. B. Floral characters: Inflorescence: Often solitary, axillary, sometimes cauliflourous in groups. Flower: Actinomorphic but zygomorphic in Monodora due to difference in size of petals, hermaphrodite, unisexual in Stelechocarpus, complete, trimerous, hypogynous, perigynous (Eupomatia) spirocyclic, often aromatic. Calyx: Sepals 3, sepaloid, polysepalous, connate at the base, valvate.: Corolla: Petals 6 in two whorls of 3 each, valvate or slightly imbricate. Sometimes no distinction into sepals and petals so perianth in 3 or more whorls of 3 each. Androecium: Stamens numerous spirally arranged on the axis which forms a large convex receptacle, filament short and thick, anthers long, extrorse, truncate connective, bithecous. Gynoecium: Carpels numerous or a few, usually free, spirally arranged on the raised receptacle, apocarpous, superior, unicarpellary, unilocular; ovules one to many, anatropous; style short or none, stigma small, Monodora (Africa) with syncarpous ovary and parietal placentation. Fruit: An aggregate of berries, united to form a single compound fruit (Annona squamosa). Seed: Large, numerous, often embedded in a copious, white fleshy pulp, endospermic. Pollination: Entomophilous, due to gaudy and scented flowers. Floral formula: Distribution of Annonaceae: The family Annonaceae is commonly called Custard-apple family. Rendle included 62 genera and 820 species in this family. Lawrence recognised 80 genera and 850 species. Takhtajan (1966) included 120 genera and 2,100 species in this family. The family is widely distributed in the tropical regions of the world. Some genera are also found in the temperate climates. In India it is represented by 129 species. Economic Importance of Annonaceae: 1. Food: The fleshy fruits of various Annona specifics are juicy and edible, and also used in preparation of soft drinks and jellies. Recent analysis shows that they contain about 18 per cent sugar. Edible fruits are also obtained from various species of Annona and Asimina. 2. Timber: Bocagea virgata, B. laurifolia, Cyathocalyx zeylanicus, Duguetia quitarensis, Oxandra lanceolata and Eupomatia laurina yield useful timber. 3. Oil: The flowers of Desmos chinensis furnish ‘Macassar oil’ a perfume. The perfume is also obtained from Mkilua fragrans and specially liked by Arab women. 4. Fibre: The bark of Goniothalamus wightii produces strong fibres. 5. Ornamental: Artabotrys odoratissimus and Annona discolor are grown in garden for their scented flowers. Desmes chinensis is an ornamental tree. Common plants of the family: 1. Annona squamosa L. – (H. Sarifa or sitafal) custard apple or sugar apple – well known fruit tree. 2. Annona reticulata L. – Bastard apple or Bullock’s heart – a fruit tree. 3. Artabotrys uncinatas – A small climbing shrub with hooked peduncles – and glabarous leaves. 4. Cyathocalyx zeylanicus (H. Hari Champa) – A tall tree with deflexed or horizontal branches. 5. Polyalthia longifolia – The. “Ashok” An ornamental tree. 6. Uvaria cordata (Dunal) – Alston is a climber noted for its cordate leaves and red flowers. Important Types of Annonaceae: 1. Annona squamosa (H. sarifa or Sitafal, Fig. 26.1): Habit: A small tree. Root: Tap, branched. Stem: Aerial, woody, branched. Leaf: Simple, alternate, exstipulate, entire, oblanceolate, obtuse. Inflorescence: Axillary, two or more flowers arise in the axil of each leaf. Flower: Bracteate, hermaphrodite, complete, actinomorphic, spirocyclic, hypogynous. Calyx: Sepals three, polysepalous, united at the base, valvate. Corolla: Petals three, polypetalous, fleshy, pale-yellow, valvate. Androecium: Stamens numerous, spirally arranged on a conical receptacle, filaments short, anthets oblong, adnated, and appendaged. Gynoecium: Multicarpellary, apocarpous, spirally arranged, superior, each unilocular, ovule one, basal placentation, style short, stigma long, tapering, papillose. Fruit: An etario of berries. Floral formula: Cucurbitaceae: General characters, Distribution, Important plants, Economic importance and Floral diagram General Information Common name: Cucumber/Pumpkin family Number of genera: This family includes 110 genera and about 640 species Propagation type: Fruit or seed Distribution: The species of this family are distributed throughout the world. In India this family is represented by about 37 genera and 97 species distributed throughout the country. The chief centre of distribution of these members is Eastern Himalayas. Vegetative characters Habitat: Members of this family are mostly mesophytes and some xerophytes are also known to exist in this family. Habit: The plants are mostly succulent, trailing, decumbent annual or perennial herbs. These plants climb by means of laterally spirally