In this article we will discuss about the classification of angiosperms.
Human interaction with the flowering plants is a fundamental biological activity. As we know all living animals even human being rely on angiosperms for substance. The world 20,000 years ago was probably much mere familiar with the local flora, in terms of species recognition than most people today because a local angiosperms flora offer a mosaic of valuable resources as food, medicine, etc.
It has always been important to be able to discuss pattern of flowering plant variation, recognize significant structural features and identify kinds. Thus the discipline of plant systematics has extremely deep cultural roots in all parts of the world.
Classification of plants is a necessity to study the number of plants available in the world.
Objectives of Classification:
Following are the objectives of classification:
1. First objective is to name all the plants of the world and fix their specificity to their habit, habitat, distribution, characters etc.
2. Second objective is to arrange them according to their characters in their particular place in the classification.
3. Name the plant according to International Code of Botanical Nomenclature in which it should have two epithets, the first in the generic name and the second is the specific name.
The ancient knowledge of Indians was very vast but their language was primarily Sanskrit which was not accessible by western people. Ancient Indians had the concept of life which can be compared to the modern one. It was given by Parashar in Vrikshayurveda.
It suggests that water transforms into kalalm (a jelly like substance) and a pindasthamukam (nucleus) is formed in it, which is regulated by terrestrial energies. The jelly is transformed into bija (germ).
They described protoplasm as Kalalibhutan (colloidal system). In their opinion plants preceded animals and man on earth. The great Indian writers Uddalaka and Yajnavalkya had thoughts of evolution and heredity even 2000 years before Darwin.
Apart of Vrikshayurveda there are several books on plant science mostly written by Varahmihir such as Brihatsamhita, Agnipurana, Sarangdhara etc.
In Vrikshayurveda, different subjects related to plants such as:
(a) Bijotptti vidhi (Seed biology),
(b) Drumraksha (Plant protection),
(c) Poshana vidhi (Agronomy),
(d) Bhumi Nirupana (Soil science), and
(e) Upavanakriya (Horticulture) etc.
There are several examples which feel that these people know about soil fertility and necessity of water, how it travels up in the trees. They know that water not only moves up but also circulate in plant body as blood circulation in human system.
Though they were not aware of the mechanism of photosynthesis yet they were knowing the importance of leaves, the role of leaves and sunlight in the sustenance of plants. They knows about the diseases of plants the remedies and prevention. Our rishis like Gunaratna, Kasyapa and Sarangdhara etc. have worked upon it.
In the book The Positive Sciences of the Ancient Hindus, King George V professor of philosophy at Calcutta University told that ancient Hindu scriptures hold the plants have dormant or latent consciousness and are capable of pleasure and pain.
Gunaratna told that plants display the phenomenon of walking and sleeping. In Mimosa pudica he observed the leaves drop by touch and he called it as Lajjalu (a shy person). Plants also show the phenomenon of life, death, sleep, diseases etc.
In Ancient Indian literature the plant and plant parts have a definite terminology. Even they have the knowledge of area, season and plant germplasm etc.
Some of the terminology is given below:
Ritus (Seasons)
Kshetra (Area)
Stambha (acaulescant)
Aprakanda (caulescent)
Skandshakha (primary branches)
Prashakha (Branchlet)
Shikhara (Apex)
Vriksharuha (Epiphytes)
Vrikshadani (Parasite)
Dwiparna (Bifid leaves)
Triparna (Trifoliate leaves)
Saptaparna (7-leaved)
Pushpadala (Petal)
Kesara (Stamen)
Paraga (Pollen)
Phala (Fruit)
Bija (Seed)
Agrabija (Buds)
Mulaj (Root)
Urvara (Fertile soil)
Usara (Sterile soil)
In ancient Indian literature the plant names are based on certain special features, characters, uses, properties, locality where they grow etc.
For example:
(A) Special properties:
1. Dadrughna (cures ring worm e.g., Cassia fistula)
2. Arsoghna (cures pils e.g., Amorphophallus paeonifolius)
(B) Special characteristics:
1. Dwipatra (bifid leaves e.g., Bauhinia)
2. Satmuli (Hundred roots e.g., Asparagus)
3. Bahupada (Many columnar prop roots e.g., Ficus)
(C) Special association:
1. Yagnadumura (Association with Yagna e.g., Ficus glome rata)
2. Bodhi druma (association with ‘Budha’ enlightenment e.g., Ficus religiosa)
(D) Uses:
1. Dhanudruma (used for making bows e.g., Bambusa)
2. Lekhana (used for making pen e.g., Arundinaria).
(E) Locality:
1. Vaidehi (indigenous to Videh or e.g., Piper nigrum)
2. Magadhi (Indiginous to Magadh e.g., Piper betal)
(F) Ecological characteristics:
1. Kutja (growing on mountain peakse.g, Holarrhena pubescens)
2. Pankeriha (grouping in mud e.g., Nelumbium)
The different species of a genus may be differentiated on the basis of the colour of flowers e.g., Pitapushpa (yellow flower), Raktapushpa (Red flower), shweta pushpa (white flowered etc.)
Ancient Indian plant classification was based on three major considerations i.e.:
(a) Udhvida (Botanical),
(b) Virechanadi (Medicinal), and
(c) Annapanadi (Dietic).
The necessacity of classification increased by the increase of knowledge of more and more plants. The classification of plants in Indian Vedas is the oldest where the saints have divided the plants based on their needs. The first literature is cited in Rigveda in 3000 BC. After that in Vrikshayurveda and Manusmriti also it could be seen. Plants were divided into 8 parts in Vrikshayurveda.
1. Oshadhi:
Medicinal annuals
2. Vanaspati:
Fruiting trees
3. Vriksha:
Fruit and flower bearing trees
4. Guccha:
Shrubs
5. Gulm:
Succulent plants
6. Trina:
Grasses
7. Pratan:
Climbers
8. Valli:
Twiners.
Such type of classification of plants is also found in Charak and Sushrut Samhita. Where the plants are classified according to their uses. In Sushrut Samhita plants are divided into 37 orders on their medicinal value.
Prasastapada (medical practioners) classified plants as:
1. Trina:
grass.
2. Oshadhi:
Medicinal herbs.
3. Lata:
Creeping herb
4. Avatanas:
Arboreal plants and shrubs.
5. Variksha:
Trees with flowers and fruits.
6. Vanaspati:
Trees with fruits but no flower.
Ancient Indian plants were studied mostly in relation to medicinal uses. In Ayurveda most of the medicinal plants with their properties and uses for different ailments are included.
The History of classification of Angiosperms is divided differently. According to one view it is classified into two major periods.
A. Pre Darwinian period and B. Post Darwinian period.
Other ways of Classification are:
1. Classification based on habit.
2. Classification based on number of floral parts e.g., stamen etc.
3. Classification based on morphological characters or form and relationship.
4. Classification based on phylogeny.
Pre Darwinian period includes the time of Theophrastus i.e., 370-285 B.C. upto the time doctrine of Darwin was proposed. However, post Darwinian period includes all the classification after the Doctrine of Organic Evolution of Charles Darwin is 1859.
Another view of classifying the history of classification of angiosperms is as:
1. Artificial system:
Based on habit or one character.
2. Natural system:
Based on morphological structure.
3. Phylogenetic system:
Based on evolutionary trends.
Artificial System:
It starts with Theophrastus (370-285 BC). Theopharstus was a philosopher and naturalist of Greece. He is also known as father of Botany. Theophrastus, a Greek student of Plato and Successor to Aristotle as Director of the Lyceum and its botanical garden.
He proposed his classification in Historia plantarum He divided the plants into:
(a) Tree,
(b) Shrubs, and
(c) Herbs.
He included about 500 plants in it.
Intellectual stagnation of the middle age resulted in minimal original work in plant systematis Albertus Magnus (1200-1800 A.D) produced a classification system for the first time recognizing Monocots and Dicots.
After a very long, gap, Otto Brunfels (1464-1534) recognized plants and named Perfecti and Imperfecti respectively to the plants with and without flower.
Jean Bauhin (1541—1631) described 5000 plants in his book Historia plantarum universalis. He was a Swiss physician. His brother Gaspand Bauhin (1560-1654) wrote a book Pinax in 1623 and described 6000 plants. Carolus Linnaeus (1707—1778) gave Sexual system of classification. He was a physician. First he published some plants in Hortus uplandicus.
Thus his most popular classification based on stamen, type, absence or presence etc. was published in Species plantarum in 1753. He diagnosed nearly 6000 species of 1000 genera.
He used binomial nomenclature of plants in the 23 volumes of Species plantarum. In Philosophia Botanica (1751), Linneaus enumerated67 “natural orders” such as Palms, Orchids, grasses, conifers, borages, composites etc. But there is a mixing of dicots and monocots in these natural orders.
Classification Proposed By Linneaus:
Linneaus divided plant kingdom into 24 Klasses:
1. Monandria (One stamen),
2. Diandria (Two stamen),
3. Triandria (Three stamen),
4. Tetandria (Four stamen),
5. Pentandria (Five stamen),
6. Hexandria (Six stamen),
7. Heptandria (Seven stamen),
8. Octandria (Eight stamen),
9. Enneandria (Nine stamen),
10. Decandria (Ten stamen),
11. Dodecandria (Twelve stamen),
12. Icosandria (Twenty stamen),
13. Polyandria (Many free stamen),
14. Didynamia (Didynamous),
15. Tetradynamia (Tetradynamous),
16. Monadelphia (One bundle),
17. Diadelphia (Two bundle),
18. Polyadelphia (Many bundles),
19. Syngenesia (Anther fused, filament free),
20. Gynandria (Stamen adnate to pistil),
21. Monoecia (Unisexual flowers on one plant),
22. Dioecia (Unisexual flowers on two different plants),
23. Polygamia (Flower Polygamous), and
24. Cryptogamia (Flowerless).
This classification was appreciated for more than 100 years. It aids to quick and easy identification of plants by means of one or few characters. The main demerit was Dicots, monocots and gymnosperm were not separated, e.g., Gynandria contain ordhids (monocot) and Passiflora (Dicots).
One genus can be placed in more than one class e.g., Brassica with six stamens is placed in hexandria as well as tetradynamia etc. Genera belonging to one family are placed in different classes.
Natural System of Classification:
It starts with.Bernard de Jussieu (1699-1777) who as centemporary of Linneaus. He was French man and professor of Botany at Royal Gardens. He modified the systems of Linneaus by dividing the flowering plants into Monocots and Dicots based on Positions of ovary, presence or absence of petals, free or fused petals etc.
His nephew Antonie Laurent de Jussieu in 1778 proposed the classification based on number of cotyledons, position, number of adhesion of petals. He published his work in Genera plantarum in 1979 and divided plants into 15 classes, 100 orders and families. He included cryptogames in Acotyledons.
Augustin P de Candolle published his classification of plants in 1819 in Prodromus systematis naturalis regni vegetabilis. Candolle published 7 volumes and his son Alphonse de Candolle continued the work and published 10 more volume, the last in 1873. The most popular and practical classification of Natural system was given by George Bentham (1800- 1884) and Joseph Dalton Hooker (1817-1911).
They jointly published their classification in Genera plantarum (in latin) in 3 volumes from 1862—83. They have taken into consideration many features of the plants. Joseph Dalton Hooker was a botanist and the first director of Kew Botanical Garden in 1865. Sir J.D. Hooker published 7 volumes of Flora of British India and Index Kewensis.
Bentham and Hooker classified only phanerogames or seed plants. They have distributed about 97,205 species in 202 families.
Bentham and Hooker’s Classification:
Bentham and Hooker divided the seed plants or spermatophytes into three divisions:
1. Dicotyledons,
2. Gymnospermeae, and
3. Monocotyledons.
Division I Dicotyledons:
It includes plants with dicotyledonous seeds, Reticulate venation of leaves and Pentamerous flowers.
It has 3 classes:
A. Polypetalae: with free petals.
B. Gamopetalae: with fused petals.
C. Monochlamydeae: Flowers have perianth i.e., calyx and corolla are either not distinguished or petals are absent.
Class 1. Polypetalae:
This class is divided into 3 series:
(a) Thalamiflorae:
Flowers with superior ovary. This series is divided into 6 orders. These are:
(i) Ranales
(ii) Parietales
(iii) Polygallineae
(iv) Caryophyllineae
(v) Guttiferales
(vi) Malvales
(b) Disciflorae:
Nectar disc is present below the ovary. Ovary is superior.
This series is divided into 4 orders.
That is:
(i) Geraniales
(ii) Olacales
(iii) Spindales
(iv) Celastrales
(c) Calyciflorae:
Flowers are generally epigynous i.e., the ovary is inferior.
This series is divided into 5 orders:
(i) Rosales
(ii) Myrtales
(iii) Pasiflorales
(iv) Ficoidales
(v) Umbellales
Class 2. Gamopetalae:
The class is divided into 3 series.
(a) Inferae:
Flowers with inferior ovary.
This series is divided into 3 orders:
(i) Rubiales
(ii) Campanales
(iii) Asterales
(b) Heteromerae:
This series is also divided into 3 orders:
(i) Ericales
(ii) Ebenales
(iii) Primulales
(c) Bicarpellatae:
Flowers with bicarpellary, syncarpous, superior ovary, epipetafous stamen. The series is divided into 4 orders:
(i) Gentianales
(ii) Personales
(iii) Polemoniales
(iv) Lamiales
Class 3. Monochlamydeae:
The flowers are either apetalous or with perianth i.e., calyx and corolla are not distinguished. Generally incomplete flowers. The class is divided into 8 series. Series are not divided into orders but directly families are assigned to it.
The Series are:
(a) Curvembryeae
(b) Multiovulate – terrestres
(c) Multiovulate-aquaticeae
(d) Microembryae
(e) Daphnales
(f) Achlamydosporae
(g) Unisexuales
(h) Ordinis anomali
Division 2. Monocotyledons:
The plants have seeds with only one cotyledon. Leaves show parallel venation and flowers are trimerous. This division is divided into 7 classes. Each class includes families directly. There is no series or order.
The classes are as follows:
(a) Microspermeae,
(b) Epigyneae,
(c) Coronarieae,
(d) Calycineae,
(e) Nudifloreae,
(f) Apocarpeae, and
(g) Glumaceae.
The classification of monocots is very unnatural. Gymnosperms are sandwiched between dicots and monocots.
Merits:
1. The classification is very practical.
2. Ranales were considered as primitive dicots.
3. Placements is gamopetalae after polypetalae also is supported by evolutionary condition.
4. Presence of Cucurbitaceae and Apiaceae at the end of polypetalae i- justified.
5. The phanerogames were divided into 202 families (cohorts) startrr: Ranunculaceae and ending in Gramineae.
6. The monocots were categorized on the basis of positions of – r – and characters of perianth.
7. In Gamopetalae, the orders start with actinomorphic f.: Bt. m and ends with zygomorphic flowers (Personales and Lamiales).
Demerits:
1. Polypetalae starts with hypogyny (Thalamiflorae) to epigyny (Calycifloreae) but Gamopetalae starts with epigyny (Inferae) and ends in hypogyny (Bicarpellatae).
2. Gymnosperms are sandwitched between Dicots and Monocots.
3. Monochlamydeae is an artificial class with a single character i.e., one whorl of perianth. Related families of curvembryae could found place in caryophyllaceae.
4. Podostemaceae is related to Rosales, and Napenthaceae to Parietales etc.
5. Retention of Nyctaginaceae, Polygonaceae, Amaranthaceae, Chenop- odiaceae etc. in Monochlamydeae is not much justified as many of them have differentiated or dichlamydous perianth.
6. Monocots starts with epigynous flowers (Microspermae and Epigyneae), while it should be taken into the last.
7. Orchidaceae has been given a primitive position though it is highly advanced in characters.
8. Closely related Liliaceae and Amaryllidaceae are kept apart in two different classes only on the basis of ovary position.
9. Monochlamydeae is divided upon series only.
10. Monocotyledons were divided into classes only.
Phylogenetic System of Classification:
The period started a little knowledge of evolution in the beginning. The authors started incorporating evolutionary bases also. In this system the first was that of August Wilhelern Eichler’s system (1839-1887). Eichler was a professor of botany in Germany. He only modified Bentham and Hooker’s system by placing Gymnosperm before angiosperms (Dicot and Monocots).
The outline is as follows:
Engler and Prantl’s Semiphylosenetic Classification:
Adolf Engler (1844-1930) Karl Pranltl (1849- 1893) published their classification in their voluminous work “Die Naturlichen Pflanzen familien”. They modified Eichler’s classification. It was the first angiosperm system which considered anatomical data also. In this the families are arranged according to increasing complexity of the flower, fruit and seed development (Fig.).
The plant kingdom is divided into 13 divisions. The 13th division was Embryophyta Siphonogama. It was again divided into Gymnospermae and Angiospmermae. Which were then divided into classes, and orders and family.
The fourteen divisions are:
(1) Schizophyta,
(2) Myxothallophyta,
(3) Flagellatae,
(4) Dinoflagellatae,
(5) Bacillariophyta,
(6) Conjugate,
(7) Heterocontae,
(8) Chlorophyceae,
(9) Charophyta,
(10) Phaeophyceae,
(11) Rhodophyta,
(12) Eumycetes,
(13) Archegoniatae,
(14) Embryophyta Siphonogama.
Archichlamydeae includes 33 orders beginning from Verticillatae and ending in Umbelliflorae with 199 families: The first family was Casuarinaceae and the last Cornaceae.
Metachlamydeae includes 11 orders staring from Diapensiales and ending into Campanulatae, with 56 families. The first family was Diapensiaceae and the last Compositae.
Naked flowers were considered as Primitive and the families were kept under Amentiferae. While dichlamydous flower was considered as advanced.
Monochlamydeae of Bentham and Hooker was abolished and generally arranged in Archichlamydeae. The group Amentiferae was treated as most primitive and begins with Verticillatae and Piperales with naked, anemophilous, unisexual flowers.
Class Monocotyledonae was divided into 11 orders starting with Pandanales and ending in Microspermae. The class contains 45 families. The 5rst family in Pandanales is Typhaceae and the 45th family in Microspermae is Orchidaceae. It means that they considered Orchidaceae as the highly evolved family.
Merits:
1. The large artificial group Monochlamydeae of Bentham and Hooker was merged in archichlamydeae.
2. Metachlamydeae or Sympetalae corresponds to Gamopetalae of Eentham and Hooker.
3. Gymnosperm are taken out from inbetween of Dicots and Monots and made separate sub division.
4. In both Archichlamydeae and Metachlamydeae the families with epigynous flowers were treated as advanced. The evolution is considered as hypogyny to epigyny.
5. Orchids were considered most advanced and evolved than grasses.
Demerits:
1. They considered the angiospermic flower as derived from gymnospermous strobilues. Primitive families bear catkin type of inflorescence (unisexual). The bisexual flower was derived from unisexual type.
2. Amentiferae is placed in the beginning of Archichlamydeae.
3. In Amentiferae, the flowers are generally naked or monochlamydous with bract like perianth.
4. They considered that Gymnosperm give rise to Amentiferae on one and monocots on the other hand.
5. Origin of angiosperm was considered as polyphyletic.
6. Primitive position of Amentiferae is critisised by many botanists.
7. Derivation of dichlamydous flower from monochlamydous was not accepted by many botanists.
8. Derivation of perietal placentation from axile placentation.
9. Monocots as more primitive than dicots.
The Englerian system positioned Coniferlike (unisexual) angiosperm at the phylogenetic base (e.g., Casuarinaceae) with taxa producing large, showy flower such as Magnoliidae as derived or specialized.
Taxa now treated as the Hamamelidae (Engler’s Amentiferae) represented the basal element and monocots are basal dicots. While this statement is abandoned by most involved with flowering plants classification.The Englerian system remain as significant cataloging device in that, due to the size, scope and quality of Die Naturlichen P flanzen familien.
The Englerian School:
Alexander Braun 1859 classified monocots on showing progression from simple to complex organization. He believed unisexual naked flower of Lamnaceae are most primitive and other originated from this with gradual complexity to Orchidaceae. In dicots he began with Apetalae → Sympetalae → ending with Leguminosae.
Eichler modified this system many a times in 1876, 1880, 1883 in the final version.
Engler and Prantl adopted this system and modified to certain extent. According to Englerian concept flower with only stamen or carpel from lowest grade of organization unisexual naked flower generally borne in Catkins are most primitive within angiosperm and probably arose from gyno-ancestors with unisexual strobilus.
Bisexual flowers are derived from a cluster of male and female flowers held together and forming a false flower (Pseudoanthum). Parianth evolved Later in evolution. This also believed in polyphyletic origin of angiosperm from gymnosperm and Ptderidophyota.
The Ranalian School:
The thought of Charles E. Bessey (1915) was modified by J. Hutchinson on angiosperm. According to which angiosperm arose from gymnosperm with female strobilus bearing megasporophyll on upper region and microspherophyll and lower region. The lower sporophylls developed with sepals and petals due progressive sterilisation. Upper one developed into stamen and Carpel.
The axis-, of strobilus condensed to from receptacle. That is why primary flower has indefinite number of perianth, stamen, free carpels, spirally arranged on receptacle. Ancestor of angiosperm was believed to be an undiscovered gymnosperm and the origin is monophyletic type.
Recent or Modern system of flowering plant classification is influenced by phylogenetic Dicots given by Charles Bessey (1845-1915) (Fig.).
Hutchinson’s Classification:
The classification based on principles of phylogeny was suggested by John Hutchinson in his 2 volumes of “The Families of Flowering Plants”. John Hutchinson was a British Botanists from England (1884-1972).
He proposed 24 principles of Phylogeny parallel to Bessey’s Dicta of phylogeny. In 19G9, he published “Evolution and Phylogeny of Flowering plants.” His other work is Genera of Flowering plants (1964-67). His classification was revised time to time (1955, 69) and finally appeared in 1973.
The main feature of classification suggests:
(1) Origin of Angiosperms is Monophyletic; originating from unknown hypothetical proangioperms.
(2) Initially Angiosperms were regarded to have evolved along two separate parallel evolutionary lines.
(a) Herbaceae (Herbaceous families starting from Ranales to Lamiales, 28 orders)
(b) Lignosae (Arborescent or woody plants starting from Magnoliales to Verbenales, 54 orders)
(c) He considered monocots to be derived from Ranales. Monocots were divided into 3 groups based on nature of Perianth into Calyciferae, Corolliferae and Glumiflorae with in all 29 orders and 104 families.
(d) In the phylogenetic tree he did not drive one order from the other. Instead, that arose from the ancestrol stock.
(e) His system provided strong basis for the later phylogenetic systems of Takhtajan, Cronquist, Dahlgreen and Thorne etc.
According to Hutchinson, the origin of Angiosperm is from Hypothetical Proangiosperms. Whereas the evolution in Lignosae is from Magnolicaceae →Verbenaceae, in Herbacae from Ranunculaceae to Lamiaceae while in
Monocotyledones from Butomaceae to Poaceae:
In the new revised classification published in 1973 small alterations were made as: Lytherales were transferred to Myrtales in Lignosae from Herbacea. Now Dicots include 82 orders and 343 families while Monocots include 29 orders and 69 families.
Merits of Hutchinsons System:
(1) It is a phylogenetic system purely based on principles of phylogeny.
(2) This system provided a base for the phylogenetic system of Ostwald Tippo; Cronquist, Takhtajan and Dahlgren etc.
(3) The system considers Ranales as primitive Herbaceous dicots while Magnoliales as primitive Lignoceous dicots.
(4) Families and orders are very small and comprises of only very much related taxa.
(5) The arrangement of families in Monocots is widely accepted.
(6) Monocots are considered to be more advanced than Dicots.
Demerits of Hutchinson’s System:
(1) Dicots were divided on the basis of habit into two major groups, i.e., Lignosae and Herbaceae. Lignosae includes woody plants. This was not accepted by many as otherwise closely related plants were kept for apart and the two evolutionary lines cannot considered distinct.
(2) The two related families on the basis of floral structure were separated, e.g., closely related families of Ranales as Ranunculaceae and Magnoliaceae were kept far away.
(3)This system did not derive one order directly from other but from ancestral stock.
(4) Several herbaceous families which are closely related or even derived from woody families e.g., Apiaceae (Herbaceous) is considered to be derived from Cornaceae and Araliaceae (woody) or Brassicaceae (Herbaceous) is derived from woody Capparidaceae via Cleomaceae.
(5) The system is not considered more useful in practical plant classification.
(6) All the emphasis has been placed on herbarium and woody habit and not on floral character.
Principles of Phyloseny given by Hutchinson: `
General:
1. Evolution is both upward and downward.
2. Evolution does not necessarily take place in all the parts of the plant at one time.
3. Evolution has generally been consistent.
Habit and Habitat:
4. Trees and shrubs are primitive than herbs.
5. In one family or genus trees and shrubs are primitive then climbers.
6. Perennials are primitive the biennials and annuals are most advanced type.
7. Aquatic plants are derived from terrestrial plants.
8. Dicots (conjoint, collateral, open, vascular bundles arranged in a ring) are primitive than monocots (conjoint, collateral, closed, scattered, vascular bundles).
Vegetative Characters:
9. Spiral arrangements (alternate) is primitive than opposite than whorled.
10. Simple leaves are primitive than compound leaves.
Floral Characters:
11. Bisexual flowers are primitive than unisexual.
12. Solitary flowers are primitive than inflorescence, Hypanthodium is most advanced type.
13. Spirocyclic flowers are primitve than cyclic.
14. Polymery is primitive than oligomery.
15. Polypetaly is primitive than Gamopetaly, similarly polysepaly is primitve than gamosepaly.
16. Apetalous flowers are derived from petaliferous flowers.
17. Actinomorphy is primitve than Zygomorphy.
18. Hypogyny is primitive than epigyny and perigyny.
19. Apocarpy is primitive than syncarpy.
20. Polycarpy is primitive than monocarpy
21. Polyandry is primitive than synandry (Adelphous to Syngenesious).
22. Cauliflory is primitive than ramiflory.
23. Endospermic seeds are primitive.
24. Simple fruit is primitive- than aggregate than Composite. Syconus is the most advanced fruit.
Dahlgren’s System of Classification:
The system was proposed by RolfM.T. Dahlgren (1932-1987) in 1974 in his book A Text-book of Angiosperm Taxonomy. The system was revised in 1975 in Botanical notiser in 1980 in Botanical Journal of the Linnearn Society; in 1981 in Phytochemistry and Angiosperm phylogeny and in 1983 in Nordiac Journal of Botany.
Dahlgren was professor at the Botanical Museum of the University of Copenhagen, Denmark. His classification is a phylogenetic classification. His classification is based on Anatomy, Phytochemistry and Embryology etc. He considered angiosperms to be Monophyletic origin angiosperms evolving from 4 Gymnosperms.
Dahlgren named Angiosperm Magnoliopsida and divided them into two subclass Magnolidae (Dicots) and Liliidae (Monocots). Magnolidae include 24 superorders, 80 orders and 346 families, and Liliidae includes 7 superorders, 26 orders and 92 families.
Merit of Dahlgren’s System:
(1) The system is a modified version of Takhtajan’s system. Data from anatomy, embryology and chemists are also considered.
(2) Dicots are considered to be more primitive than Monocots.
(3) Dahlgren illustrated his system as a phylogenetic shrub showing the relationship between orders. (Fig. 2).
Demerits of Dahlgren’s System
(1) Dahlgren made many unnatural orders and Superorders.
(2) He did not consider the Polyphyletic origin of Angiosperms from Gymnosperms.
(3) Dahlgren thought that 8 nucleate embryosac, companion-cell in phloem and secondary endosperm etc. have evolved independently.
(4) Nomenclature of various groups are criticized and the name Pseui suggested for a conjectural taxon.
Robert Thorne’s System of Classification:
Robert F.Thorne published his Phylogenetic type of classification as “a synopsis of a pultatively phylogenetic system of classification of flowering plants” in Aliso in 1968. He first proposed some phylogenetic guidelines and then elaborated his classification in 1976. He revised the classification in 1981 and published in Phytochemistry and Phylogeny and in 1983 in Nordiac Journal of Botany.
He included data form Phytochemistry, host- parasite relationships, pollen and seed morphology, comparative anatomy, microstructure, embryology, plant geography, palaeobotany and cytology in his classification. He believed that the origin, Angiosperms is Monophyletic. He divided Angiospermae (Annonopsida) in two subclass Dicotyledoneae (Annonidae) and Mono- cotyledoneae (Liliidae).
He divided Subclass Annonidae into 19 super-orders, 41 orders, 56 suborders, 297 families, 350 subfamilies 9640 genera, 1, 73,370 species and Subclass Liliidae into 9 Superorder 12 Orders, 17 Suborders, 53 families, 102 subfamilies, 2,615 genera and 52,120 species.
Robert F. Thorne revised his classification in “Classification and Geography of Flowering Plants” Which was updated once again in 1999 March.
According to which the classification is as follows:
Merits of Thorne’s System:
(1) Annonales are considered as primitive living angiotperms.
(2) Closely related taxa are placed nearer to one another.
(3) Orders Cornales and Dipsacales are placed under one superorder Corniflorae.
(4) Families of Amentiferae are distributed into different orders.
(5) Orders Malvales, Urticales, Rhamnales and Euphorbiales are included in one superorder Malviflorae (Fig. 3).
Demerits of Thorne’s System:
(1) The unnatural super-orders and suborders, subfamilies are much in number.
(2) It is not practical in identification of plants.
(3) Throne’s view was that angiosperms originated from some Pteridospermous members in early cretaceous period is not accepted by many taxonomists.
Armen Takhtajan’s System of Classification:
Armen Takhtajan was born in 1910. He was Head of Department of higher plants at Komarov Botanical in Leningrad (Russia), when his classification was first published in 1942. In 1959 in elaborated system of classification appeared in German in his “Die Evolution der Agniospermen” in 1966. He modified the classification and published in English in Flowering Plants; Origin and Dispersal.
In 1980 A new version of his classification appeared in Botanical review. Takhtajan’s system is basically inspired by Bassey- Hallier tradition considering evidences from fields like Morphology, Anatomy, Embryology, Cytology, Palynology, Paleobotany, Chemistry, Ultrastructure etc. According to Takhtajan angiosperms are monophyletic in origin and have derived their ancestry from Gymnosperms. Monocots are derived from primitive dicots.
In 1980 Takhtajan divided Magnoliophyta (Angiosperms) into 2 classes Magnoliopsida and Liliopsida with about 10 Subclasses (7 in Megnoliopsida and 3 in Liliopsida).
In 1977 he revised his classification and now the two classes include 151 subclasses (11 in Magnoliopsda and 6 in Liliopsida). These are as follows:
According to Takhtajan among Magnoliopsida, Magnoliidae is the most primitive basal group from which others are derived and Asteridae is the most advanced one. However, in Liliopsida, Alismatidae, Lilidae and Arecidae are considered to be more primitive than the other subclass of Magnoliopsida, and have been derived from Magnolidae. Winterceae was considered to be the most primitive family and Poaceae to be the most advanced family among angiosperms.
Takhtajan’s system is based on some Phyletic principles.
The most important on which his classification was based are as follows (Fig. 4):
(1) Woody plants are more primitive than herbaceous plants.
(2) Deciduous woody plants are evolved from evergreen plants.
(3) Xylem fibres evolved from tracheids to libriform fibres, through fibre tracheids.
(4) Trilacunar or pentalacunar nodes are primitive to unilacunar nodes.
(5) Alternate leaf phyllotaxy is more primitive than other types.
(6) Parallel venation is advanced.
(7) Anomocytic stomata (Stomata without subsidiary cells) are more advanced than stomata with subsidiary cells.
(8) Cymose inflorscence is more primitive than recemose.
(9) Flowers with an indefinite or variable number of floral parts (Polymerous) are primitive.
(10) Pollen with unsculptured exine (smooth) is more primitive than sculptured exine.
(11) Apocarpous gynoecium is more primitive than syncarpous.
(12) Bitegmic ovules are primitive than unitegmie ovules.
(13) Anatropous ovule is more primitive than others.
(14) 8-nucleated Polygonum type embryosac (female gametophyte) is most primitive.
(15) Mesogamic and chalozogamic conditions have evolved from porogamic condition.
(16) Many seeded follicle fruits are most primitive.
Merits of Takhtajan’s System:
(1) Magnoliopsida is considered primitive to Liliopsida,
(2) Families are small in size and made up of every closely related genera.
(3) Dicots start with most primitive Magnoliales.
(4) Monocots start with most primitive Alismatales.
(5) Problems of Monophyly or Polyphyly, Inter-relationships of monocots and Dicots etc. are dealt satisfactorily.
Demerits of Takhtajan’s System:
(1) Derivation of Monocots from the stocks ancestral to the Nymphaeales.
(2) Extremely narrowly defined taxa have resulted in the unwarranted splitting of related groups.
Arthur Cronquist’s System of Classification:
Arthur Cronquist’s was born on March 19, 1919 in San Jose, California. He joined the University of Idaho with Prof. J Davis. He worked under the direction of Dr. Basselt Maguire on Aster Foliaceus complex. He worked at New York Botanical Garden in 1943. He left the Botanical garden in 1951 and joined Washington State University to teach Botany.
Again, he joined back the New York Botanical Garden in 1952 and worked on floristics with Henry A. Gleason. They published “New Britton and Broswon illustrated flora in 1952.
The second book was published with Gleason named Manual of Vascular Plants of Northeastern United Arthur Crofnquist (1919-92) States and Adjacent Canada in 1963; “The Natural Geography of Plants” in 1964.
Cronquist worked as Director of Botany from 1971-74 and Senior Scientist from 1974-92 at the New York Botanical Garden. He was president of American Society of Plant Taxonomists in 1962, Botanical Society of America in 1973, and Torrey Botanical Club in 1976. He received many Awards also.
He received Asa Gray Award of American Society of Plant Taxonomists in 1985, Medal for Botany from Linnean Society of London in 1986. He died on March 22, 1992 while studying plant specimens in the herbarium of Brigam Young, University in Utah.
The first classification of Dicotylodons was presented in 1957 by A. Cronquist. It was modified in 1966, 1981 and finally published in 1988 in his book Evolution and Classification of Flowering Plants. The first revision in 1966 with Sporne and Zimmerman. In 1968 the classification was published in a book called Evolution and Classification of Flowering Plants.
In 1981 it was again revised and appeared in Integrated Systematics of Classification of Flowering Plants. The classification is based on observations and discussions with other botanists. Classification is based on evidences from Morphology, Anatomy, Embryology, Palynology, Serology, Phytochemistry, Cytology etc.
Important Features of Classification:
1. Traditional nomenclature of angiosperm, dicots and monocots is replaced as has been done by Takhtajan.
2. Synthetic system of classification taken help from other fields of botany to deduce his interpretation.
3. Key for each group upto family is useful.
4. System appears more natural.
5. Evolution relationship amongst the subclasses of dicots has shown in the form of balloon. The size of balloon is proportionate to member of species in each group (Fig. 5).
Cronquist divided Angiosperms Magnoliophyte into 2 classes Magnoliopsida and Liliopsida. Classes are divided into subclass, orders and families. No super orders are formed. Magnoliopsida is divided into 6 subclasses and Liliopsida is divided into 5 subclasses.
Merits of Cronquist’s Classification:
1. It is a phylogenetic classification.
2. He compared all the previous classification and discussing their merits and demerits proposed a new classification.
3. He considered morphology, anatomy, embryology, palynology, serology, cytology, and phytochemistry in his classification.
4. Key for each group upto families is useful.
Demerits of Cronquist’s Classification:
1. Arrangement of some families in Liliales is criticized.
2. Submergence of Amaryllidaceae into Liliaceae is not satisfactory.
3. It shows too much reliance on single character, e.g., free central placentation and centifugal stamen etc. many times which is not accepted.
4. Traditional nomenclature is replaced.
Differences between Magnoliopsida and Liliopsida:
Magnoliopsida:
1. Dicots,
2. Reticulate Ventation,
3. Roots primary and adventitious,
4. Vascular Cambium present,
5. Vascular bundles arranged in a ring in stem,
6. Flower Tetra or Pentamerous, and
7. Pollen grains of various types.
Liliopsida:
1. Monocots,
2. Parallel venation,
3. Roots only adventitious,
4. Vascular Cambium absent,
5. Scattered Vascular Bundles in stem,
6. Flowers usually Trimerous, and
7. Pollen grains mainly monosulcate types.
Important Characters of Different Subclasses Magnoliopsida
Subclass 1 Magnoliidae:
It includes 8 orders, 39 families. The families show primitive characters. Plants generally are woody (shrubs or arborescent). Leaves evergreen, stipulate or existpulate simple, alternate.
Flowers solitary, actinomoprhic, polymerous, floral axis elongated. Calyx and Corolla not much distinct, i.e., generally perianth. Numerous stamens with laminar to terete filament. Numerous carpels, apocarpous. Fruits generally follicle entomophilous.
The orders start from Magnoliales to Papaverales (herbaceous, syncarpous plants).
Subclass 2. Hamamelidae:
It includes 11 orders and 24 families. Typically plants are woody except order Urticales. Flowers are unisexual (imperfect); perianth apetalous (absent) or reduced, inflorescence with numerous reduced apetalous flowers arranged in catkin or ament. The group as named is Amentiferae.
Primitive order is Trochodendrales and advance is Casurinales (multiple fruiting structures).
Subclass 3. Caryophyllidae:
It includes 3 orders, 14 families. Caryophyllales in the largest order. The plants in this order lack anthocyanin instead possess Betalins (Betacyanin and Betaxanthin). Betalins are otherwise found in fungi only. Perianth is uniseriate. Placentation is either basal or free central.
The older name of the group is Centrospermae as the ovules are present around in placenta in the centre of the ovary. In most of the caryophyllales perisperm is present which is derived from sporophytic tissue (2N) instead of endosperm. Embryo takes a peripheral position in the seed and produced a Beaked (protrusion of radial)
The families start from Phytolaccaceae to Caryophyllaceae come under the order caryophyllales.
The 3 orders are Caryophyllales, Polygonales and Plumbaginales.
Subclass 4. Dilleniedae:
This subclass includes 13 orders and 78 families. The plants show diverse characters. All the plants have synacarpous flowers except Dilleniales where flowers are apocarpous. Generally perietal, free central axile or basal placentation and Gamopetatous flowers.
Rarely they are poly or apetalous flowers. Lack of connection in gynoecium, e.g., Paeonia-Paeoniaceae order Dilleniales. Dilleniales from a link between Dileniidae and Magnoliidae. It starts form Dilleniales order and ends in Primulates. Dillenidae is divided into Pinnate Dilleniales and Palmate Dilleniada.
Subclass 5. Rosidae:
It includes 18 orders 114 families. It is the largest subclass. It includes flowers with diverse characters. Generally the leaves are pinnately compound, polypetalous, very rarely gamoptalous, nectary disks are present, Gynoecium generally synacarpous, Apocarpous in Fabales and Proteales, and apocarpous- synacarpous in Resales. Placentation marginal, Basal or Axial. Orders start from Rosales to Apiales.
Flowers hypogynous → Perigynous → Epigynous, Polypetalous or basally connate or reduced, nectarias often staminodal in origin, frequently from intra or extrastaminal disc.
Stamen initiate in centripetal sequence (except Punicaceae), Gynoecium apocarpous in monocarpellary condition as in Fabales, Proteals etc. Many Rosales have syncarpous gynoecium with ovary sperior semi inferior → inferior condition. Placentation varies but majority its in axile less commonly parietal or basal.
Subclass 6. Asteridae:
Subclass includes 11 orders and 49 families. One third of the total plants belong to Asteraceae. Flowering actinomorphic or zygomorphic hypogynous- epigynous……. gamopetalous; Gynoecium 2-5 carpels synacarpous, usually are necterifereous disc is style terminal or gynobasic with basal to axial placentation and stamens epipetalous.
Asteridae is considered to be most advanced dicotyledonous plant. Some of the orders included in it are hypogynous to the Advanced Asteraceae as epigynous. The order starts from Gentianales to Asterals.
Liliopsida:
Subclass 1 Alismatidae:
Subclass Alismatidae includes 4 orders and 16 families. It is considered to be the smallest subclass of Magnoliophyta. Gynoecium 1-α and apocarpous. It may be 2-3 carpels fused below forming pseudomonomerous unilocular. Generally aquatic plants except Triuridales. Orders start from Alismatales to Triuridales. Subclass is considered to be nearer to Magnoliidae through Nymphaeales.
Subclass 2. Arecidae:
It includes 4 orders and 5 families. Flowers small often crowed in spadix, hypogynous, ovary sunken in axis. It includes smallest flowering plants (Lemnaceae) in Arales and the largest monocots (Arecaceae) in Arecales. Largest Angiospemic seed is Lodoicea maldivica belongs to Arecaceae. The largest leaves of Raphia regalis are also considered in Arecaceae. The order starts from Arecales to Arales.
Subclass 3. Commelinidae:
It includes 7 orders and 16 families. Flowers bi or unisexual hypogynous nectaries rarely present pollination by wind, Trimerous apomicts. It includes the largest monocot family, the grasses Poaceae. The family is economically as well as ecologically very important. Flowers entomophilous to anemophilous. The orders follow a phyletic pattern. The orders start from Commelinales, to the Typhals.
Subclass 4. Zingiberidae:
The subclass includes 2 orders and 9 families. The two orders are Bromeliales and Zingiberales. Bromeliales show diverse characters. Bromeliales is a monotypic order including epiphytes. Flowers are actinomorphic trimerous hypo or epigynous and hexandrous. In Zingiberales plants are mesophytes with zygomorphic, 6 stamens but 1-5 stamens are functional in flowers. Sometimes flowers are functionally unisexual. They are Bird or Bat pollinated.
Subclass 5. Liliidae:
The last subclass includes 2 orders and 19 families. Flowers are very large and showy; generally petaloid sepals. The orders are Liliales and Orchidales. Liliales include actinmorpic flowers with superior or inferior ovary. Orchidales are characterized by mycotropic plants, epiphytes, flowers, zygomorphic with inferior ovary numerous seeds, anemophilous pollination and non-endospermic embryo.
Angiosperm Phylogeny Group (APG) System:
Recent cladistic analyses have revealed that the phylogeny of Angiospems is supported for monophyly by many major groups above the family level. With many elements of the major branching scheme of phylogeny of these groups being established by now, a revised suprafamilial classification of flowering plants becomes both feasible and desirable.
APG system organizes plants into a “selected number of monophyletic suprafamilial groups”. The system was proposed in “An ordinal classification for the families of flowering plants” in 1998 and 2003 in “The Annals of the Missouri Botanical Garden” Compiled by Kare Bremer, Mark W. Chase and Peter F. Stevens, et al.
Based on a cladistic methodology, the grouping presents in this system are viewed by the authors as monophyletic clades. The higher levels are described as in informal and many families and orders are unassigned to higher level grouping.
The classification shows 462 families in 40 putatively monophyletic, order and a small number of monophyletic informal higher groups. The latter are monocots, commelinoids, eudicots, core eudicots, rosids including eurosids I and II and asterids including euasterids I and II. Informal groups include a number of families without assignment to order.
At the end of system an additional list of families of uncertain position is given for which no firm data exist regarding placement anywhere within the system. Phylogenetic naming is adopted as under current International Code of Botanical Nomenclature (Greuter et al. 1994).
Principle of priority is not mandatory for texa above the rank of family but the authors tried to balance priority with general usage while assigning names to orders. Generally, the well known orders are retained with the discoveries of new species, genera, and families, the size of genera, families, and orders have increased and many orders are now comprised of 10—20 families or even more.
A number of small orders are also recognised because these represent clades for which monophyly and relationships are well supported. It better conveys the interrelationships of the families included rather than leaving them unclassified to order. APG group recognises 462 families and 40 orders while Cronquist (1981) recognised 321 families 64 orders. Thorne (1992) 440 families and 69 orders, Takhtajan (1997) and 589 families in 232 orders.
In this ordinal classification, the principle of monophyly in combination with their desirability of maintaining already well established and familiar entities has largely been considered. Monofamilial orders and monogeneric families are avoided minimizing redundancy in classification.
Some monofamilial orders, e.g., Ceratophyllales, Accorales and Arecales are recognised because these are sister groups of more than one order. So, the families of these monofamilial order cannot be included in any other order without isolating monophyly.
Monophyly Principle in combination with mandatory usage of the family category leads to the recognition of many families, e.g., In Dipsacales, if Dipsacaceae and Valerianaceae are to be retained as families from Caprifoliaceae, the principle monophyly requires the recognition also of Diervillaceae, Linnaeaceae and Morinaceae because each of these families is the sister group of more than one family, so they cannot be merged with other family without violating monophyly.
These are small families that may be reduced to synonymy of their sister group if the latter consists of a single family., e.g., Cabombaceae may be merged with Nymphaeaceae, and Kingdoniaceae may be merged with Circaesteraceae (Ranunculales).
Some families may be non-monophyletic, revised circumscriptions, either by merging or splitting, into monophyletic taxa, e.g., Euphorbiaceae and Flacourtiaceae of Malpighiales; several families of Myrtales, core Caryophyllales comprising of Achatocarpaceae, Aizoaceae, Amaranthaceae. Basellaceae, Cactaceae, Caryophyliaceae, Didiereaceae, Molluginaceae, Nyctaginaceae, Phytolaccaceae, Portulaccaceae, Sarcobalaceae and Stegnospermataceae.
The APG classification gives a major difference in the expansion of Alismatales including Araceae, Caryophyllales including Droseraceae, Nepenthaceae, Polygonaceae, Plumbaginaceae etc.
The recognition of a comparatively widely circumscribed Rosales including Rhamnaceae. Urticaceae, Moraceae etc. in addition of a number of smaller orders like Ceratophyllales, Acorales, Arecales, Proteales Carryales, Aquifoliales, and in deletion of Aristolochiales, Nymphaeales, Bromeliales, Trochodendrales, Zygophyllales etc. Monocots and Eudicots are not formally ranked and named.
Figure 2 explains the inter-relationships among the basal branches of the tree and the position of the root of the flowering plant phylogny remain elusive.
Under each of the superaordinal groups of monocots, commelinoids, core eudicots, rosids etc., there are a number of families listed without assignment to order as their ordinal position is still uncertain. Amborellaceae, Austrobaileyaceae and Canellaceae are listed at the beginning as they belong in neither any of the phylogenetically based orders at the beginning nor in the monocots or eudicots.
Families listed directly under monocots without an order are monocots and not commelinoids, families listed directly under Eudicots and Core-eudicots are Eudicots oe Core eudicots and not Rosids or Asterids. The families listed in the last are of uncertain position. They are probably eudicots.
Comparison between Bentham and Hooker, Engler and Prantl and Hutchinson’s Classification
Bentham and Hooker:
1. The system was proposed in “Genera plantarum.”
2. The system was published in 1862.
3. It is a natural system of classification.
4. This system was based on de Candolle’s system (1818) which was the modification of Jussieu’s system.
5. Flowering plants are divided into Dicotyledons Gymnospermae and Monocotyledons.
6. Flowering plants were divided into 202 families.
7. Gymnosperms are placed between Dicots and Monocots.
8. Dicots kept before monocots.
9. Dicots divided into three classes polypetalae, Gamopetalae, and Monochlamydeae.
10. Dicots were further divided into series, order etc.
11. Monocots were divided into 7 classes, no orders.
12. Polypetate is divided into 3 series. Thalamiflorae, Disciflorae and Calyciflorae. Polypetalae has 15 orders starting with Ranales to Umbellales.
13. Gamopetalae is divided into 3 series Inferae, Heteromerae and Bicarpellatae. It has 10 orders starting with Rubiales to Lamiales.
14. Cucurbitaceae with gamopetalous flowers is included in Passiflorales of Polypetalae.
15. Highly evolved Asteraceae is placed in the beginning of Gamopetalae in the series Inferae and order Asterals.
16. Orchidaceae is placed in the beginning of Monocots in class Microspermae.
17. Gramineae is considered most advanced and placed in the end of Monocots.
Engler and Prantl:
1. The system was published in Die naturalichen pftenzen familien.
2. The system was published in 1931.
3. It is semi-phylogenetic system.
4. The system was modification of Bentham and Hooker’s system where Monochlamydeae is merged into Archichlamydeae. It is based on Eicher’s system mainly.
5. Flowering plants called Embryophyta siphonogama has been divided into Gymnospermae and Angiosprmae.
6. Flowering plants were divided into 280 families.
7. Gymnosperms are placed before angiosperms.
8. Monocots kept before dicots.
9. Dicots divided into Archichlamydeae and Metachlamydeae.
10. Dicots were divided directly into orders.
11. Monocots were divided into orders.
12. Archiclilamydeae divided into 31 orders starting with Vertioillate and ending with Umbelliflorae. Amentiferae is the primitive group.
13. Sympetalae is divided into 11 orders starting with Dispansiales to Companulatae.
14. Cucurbitaceae is placed in Cucurbitales of Sympetalae.
15. Asteraceae is placed in Sympetalae and the last order Campanulatae.
16. Orchidacae is placed at the end of Monocots under order Microspermae.
17. Gramineae is placed between Heiobiales and Princeps in the order Glumiflorae.
Hutchinson’s:
1. The system was published in “Families of flowering plants.”
2. The system was published in 1959.
3. It is purely a phylogenetic system.
4. This system was based on 24 principles of Phylogeny suggested by him. The Dicots are not divided on petal position. Dichlamydous plants where considered primitive.
5. Angiosperms are divided into Dicots and Monocots.
6. Flowering plants were divided into 411 families.
7. Same as Engler and Prantl’s system.
8. Dicots are kept before monocots.
9. Dicots are divided into Lignosae and Herbaceae.
10. Direct order as
11. Monocots were divided into calyciferae, corolliferae and glumiflorae.
12. Lignosae is divided into 54 orders. It starts with Magnoliales end with Verbenales.
13. Herbaceae is divided into 28 orders, starting with Ranales to Lamiales.
14. Cucurbitaceae is placed in Lignosae in the order Cucurbitales.
15. Asteraceae is placed in Herbaceae under Asterales.
16. Orchidaceae is placed as the last family of Corolliferae.
17. Gramineae is placed in the last under Glumiflorae.
Five Kingdom Classifications:
Living organisms are subdivided into 5 major kingdoms including Monera, Protista (Protoctista), Fungi, Plantae and the Animalia. Each kingdom is further subdivided into separate Phyla or divisions. Generally Animals are subdivided into Phyla while plants into Division. Living have two major characters the prokaryote and eukaryote.
A. Prokaryotic Cells without Nuceli and Membrane bound organelle
1. Kingdom Monera [10,000 Species]:
Unicellular and colonial including the true Bacteria (Eubacteria) and Cyanobacteria (Blue-green algae).
B. Eukaryotic Cells with nuclei and Membrane bound organelle
2. Kingdom Protista (Protoctista) [250,000 Species]:
Unicellular protozoan; unicellular and multicellular macroscopic algae with 9+2 cilia or flagella or undulopodia.
3. Kingdom Fungi [100,000 Species]:
Haploid and diKaryotic (binucleate) cells, multicellular; generally heterotrophic without cilia and eukaryotic (9+2) flagella (undulopodia).
4. Kingdom Plantae [2,50,000 Species]:
Haplo-diploid life cycles, mostly autotropic, retaining embryo within female sex organ on parent plant.
5. Kingdom Animalia [10,00000 Species]:
Multicellular animals, without cell walls and photosynthetic pigments, forming diploid blastula.
The discovery of Archaebacteria complicated this classification as it is different from eubacteria and cyanobacteria included in Monera. Lipids of Archeo-bacterial cell membrane is different from prokaryote and eukaryote cell membrane. The cell wall composition is different.
The sequence of its rRNA subunit is also different. Recent studies show that archaebacterial RNA polymerases resemble the eukaryotic enzymes, not the eubacterial RNA polymerase. Archaebacteria have introns in some genes like advance eukaryots.
Some scientists put Archaebacteria in separate kingdom making 6 Kingdom classification. The data from DNA and RNA comparison indicate that Archaebacteria are so different that it cannot be classified with bacteria. Systematists daised a classification level higher than kingdom, called a domain or Superkingdom to accommodate Archaebacteria. Now it is placed under domain Archaea.
Now there is seven kingdom classification suggested. It is based on molecular evidence base sequences from ribosomal RNA.
Guillaume Le Cointre and Herve Le Guyader (2006) published a book The Tree of Life: A Phylogenetic Classification. It includes the three major domains which are in turn subdivided into numerous branches (Clades).