This ppt explains about the history of plant taxonomy, about different types of classification systems, their merits, demerits, principles, etc.

1. History & Development
of Plant Taxonomy
Prepared by-
Dr. Sangeeta Das
Assistant Professor
Department of Botany
Bahona College
Jorhat, Assam, India.

2. People who contributed….
Herbalists & Agriculturalists- passed knowledge
on plants from generation to generations.
Theophrastus (372-287 BC), the Greek
philosopher-scientist, called the “Father of
Botany” placed this knowledge of plants on a
scientific footing. In his “Enquiry into Plants” he
dealt with the plants at large and attempted to
arrange the plants in several groups.

3. Pliny compiled a monumental work entitled
“Historia Naturalis” where he incorporated all
information about plants gathered up to that
time.
Disocorides was a contemporary of Pliny and
like him travelled a lot and gathered
information about medicinal plants and
compiled his famous book “Materia Medica”.
People who contributed….

4. By the end of 15th century, a few German herbalists
contributed for the deveopment of plant taxonomy.
Otto Brunfels published his book “Herbarium vivae
Eiconis” in three volumes (1530-1536) with good
figures.
Jerome Bock (1498-1554), published his book “Nue
Kreuterbuch” with descriptions of about 600
species of flowering plants and classified them into
3 major groups, viz., herbs, shrubs, and trees.
People who contributed….

5. Andrea Caesalpino (1519-1603) also
classified the plants on the character
of their habit, viz., trees, shrubs, and
herbs but also took into account the
characters of ovary, fruit, and seeds
and published his famous book “De
plants” in 16 volumes, the first of
which contained his principles of
classification.
John Ray (1627-1705).
People who contributed….

6. John Ray, an English naturalist (1628-1705), was the
first to recognise 2 major taxa of flowering plants, viz.,
Dicotyledons and Monocotyledons.
• He divided the plant kingdom first into 2 groups, viz.,
Herbae and Arbores. The Herbae were then divided
into Imperfectae and Perfectae, the first of which
included the Cryptogams and the second group, i.e.,
the Arbores included most of the flowering plants.
• The Perfectae were subdivided into Dicotyledonae and
Monocotyledonae and under Dicotyledonae he placed
25 of his classes and 4 under Monocotyledonae and
published in his “Historia plantarum”.
People who contributed….

7. Carolus Linnaeus (1707-1778), a Swedish naturalist,
proposed a system of classification in his book
“Systema Naturae” (1735).
He used the character of stamens, i.e., the number and
nature of stamens, to distinguish the 20 classes in
which he divided the plant kingdom. He also used the
number and nature of carpels to distinguish the orders,
i.e., subdivisions of his classes.
He further used Binary System of nomenclature
published in “Species plantarum” (1753).
People who contributed….

8. The modern taxonomists have agreed to consider
the year 1753 as the starting point of
nomenclature of Phanerogams, Pteridophyta, and
Sphagnum. In his “Philosophia Botanica” he laid
down some principles which later formed the basis
of the International Code of Botanical
Nomenclature (ICBN).
Due to the efforts of C. Linnaeus the study of
Botanical science entered the modern age and
Linnaeus is called the “Father of Modern Botany”.
People who contributed….

9. There are three types of system of plant
classification. They are:
1. Artificial Classification
2. Natural Classification
3. Phylogenetic Classification.
Systems of Plant Classification

10. • It is the earliest systems of plant classification, e.g. e.g.
systems of Theophrastus, Dioscorides, etc.
• It remained dominant from 300 B.C. up to about 1830.
• It was based on one or a few easily observable characters of
plants, such as habit (trees, shrubs, herbs, etc.) or floral
characters (particularly the number of stamens and carpels).
• Such types of classification using some arbitrary or at least
easily observable characters, often irrespective of their
affinity, is called artificial.
• The sexual system of Linnaeus is a good example of artificial
classification, which uses only one attribute i.e. the number
of stamens for grouping plants into 24 Classes as a result of
which, various unrelated taxa, which are not at all related but,
similar in one respect only, have been placed under the same
Class.
Artificial System of Plant Classification

11. These systems of classifications are based upon
overall resemblances, mostly in gross morphology,
thus, utilizing as many taxonomic characters as
possible, to group taxa.
Classifications proposed by John Ray, Benthum &
Hooker, etc. were based on natural principles of
plant classification.
Natural System of Plant Classification

12. It started in 1859 following the publication of
‘Origin of Species’ by Charles Darwin.
They used as many taxonomic characters as
possible in addition to the phylogenetic
(evolutionary) interpretations.
These are expressed in the form of phylogenetic
trees or shrubs showing presumed evolution of the
groups.
Classifications proposed by Hutchinson, Takhtajan,
etc. were based on phylogenetic prinipes of plant
classification.
Phylogenetic System of Plant Classification

13. The natural systems are two-dimensional
i.e. based on the data available at any
time and is known as Horizontal
Classification
Whereas the addition of the third
dimension i.e. past history or ancestral
history results in phylogenetic
classification also known as Vertical
Classification or Evolutionary
Classification.

14. The outline of Linnaeus System of classification with twenty four
(24) classes is given:
Classes:
1. Monandria (flowers with 1 stamen).
2. Diandria (flowers with 2 stamens).
3. Triandria (flowers with 3 stamens).
4. Tetrandria (flowers with 4 stamens).
5. Pentrandria (flowers with 5 stamens).
6. Hexandria (flowers with 6 stamens).
7. Heptandria (flowers with 7 stamens).
8. Octandria (flowers with 8 stamens).
9. Enneandria (flowers with 9 stamens).
10. Decandria (flowers with 10 stamens).
11. Dodecandria (flowers with 12 stamens).
12. Icosandria (flowers with more than 20 stamens are attached to
the calyx).
Linnaeus’s Sexual system of Classification

15. 13. Polyandria (flowers with more than 20 stamens are attached
to the receptacle).
14. Didynamia (stamens didynamous).
15. Tetradynamia (stamens tetradynamous).
16. Monadelphia (stamens monadelphous).
17. Diadelphia (stamens diadelphous).
18. Polyadelphia (stamens polyadelphous).
19. Syngenesia (stamens syngenesious).
20. Gynandria (stamens adnate to the pistil).
21. Monoecia (plants monoecious).
22. Dioecia (plants dioecious).
23. Polygamia (plants polygamous).
24. Cryptogamia (non-flowering plants i.e., cryptogams which
include algae, fungi, mosses and ferns).
Linnaeus’s Sexual system of Classification

16. Merit:
The only merit of this system is the quick and easy identification of
plants based on one or a few characteristics.
Demerits:
1. This system was developed on differences rather than on similarities
of sex organs.
2. The closely related members go apart and the distantly related
members become very close to each other.
3. The Gymnosperms were placed in the 14th class Didynamia along
with Labiatae, an angiosperm family.
4. The Monocotyledons, Dicotyledons and Gymnosperms i.e.,
phanerogamic plants are not considered separately.
5. Thus it can be said that this classification is just like a dictionary where
the words are arranged alphabetically without maintaining any
relationship.
Merits and Demerits of the Linnaeus system are..

17. George Bentham and Joseph Dalton Hooker’s System

18. 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.
Salient Features of Bentham and Hooker’s system:

19. 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.
Salient Features of Bentham and Hooker’s system:

20. Merits:
1. This is a great natural system of its own kind.
2. This one is suitable for all practical purposes especially
for identification and description of plants.
3. Beginning of the Subclass Polypetalae with the Cohort
(= Order) Ranales, comprised of Ranunculaceae and its
allied Natural Orders (= Families).
4. The Dicotyledons are primitive than Monocotyledons.
5. They have studied the actual specimens available at
that time and represented them in the classification
after careful comparative examination.
Merits and Demerits:

21. 1. The classification is based on the assumption of constancy of
species. Hence, closely related Cohorts (= Orders) are often
widely separated.
2. Authors were silent about the phylogeny of Dicotyledons and
Monocotyledons and the anomalous position of
Gymnosperms in between Dicotyledons and
Monocotyledons.
3. The authors did not consider the phylogenetic relationship.
4. In Monocotyledons, they placed Scitamineae and
Orchidaceae at the very beginning. But these should not be
regarded as primitive with so many advanced characteristics.
5. In the Class Monocotyledons proper emphasis has not been
given on:
i. The relative position of ovary, and
ii. Characteristics of the perianth.
Demerits..

22. Adolf Engler (1844-1938) and Eugen Prantl (1849-
1893) proposed this phylogenetic system of
classification.
According to this system the families were arranged
in accord to the increasing complexity of the flower,
fruit and seed development.
The general outline of the system proposed by
Engler and Prantl is given below.
Engler and Prantl’s System of Classification:

27. Merits and Demerits of Engler and Prantl’s
System of Classification:
Merits:
1. According to this system, the large artificial group
of Bentham and Hooker’s system, the
Monochlamydeae has been completely abolished.
2. In this system the Gymnosperms are treated
separately.
3. The Sympetalae of this system corresponds to the
Gamopetalae of Bentham and Hooker’s system.
4. They considered the orchids to be more highly
evolved than the grasses.

28. Demerits:
1. In this system, the Amentiferae or catkin bearers,
(e.g., Salicaceae, Juglandaceae, Betulaceae, etc.)
have been regarded as most primitive.
2. The acceptance of the derivation of dichlamydeous
flowers (perianth in two series) from
monochlamydeous ones (perianth in single series)
is objectionable.
3. In this system Monocots have been considered to
be more primitive than Dicots, which does not
correspond to the present day knowledge.
4. Derivation of bisexual flowers from unisexual
flowers.

29. John Hutchinson’s System of Classification
John Hutchinson (1884-1972) an English botanist
has given the latest information about the
phylogenetic classification of angiosperms which
has been published in his famous work, “Families of
Flowering Plants” recently in 1959.

30. The following principles were adopted by
Hutchinson to classify the flowering plants:
1. Evolution takes place in both upward and
downward direction.
2. During evolution all organs do not evolve at the
same time.
3. Generally, evolution has been consistent.
4. Trees and shrubs are more primitive than herbs in a
group like genus or family.
5. Trees and shrubs are primitive than climbers.

32. He divided the Phylum Angiospermae into two
Subphyla Dicotyledones and Monocotyledones. The
Dicotyledones are further divided into two divisions —
Lignosae (arboreal) and Herbaceae (herbaceous).
The Lignosae includes, fundamentally, the woody
representatives derived from Magnoliales and
Herbaceae includes most of the predominantly
herbaceous families derived from Ranales. The
subphylum Monocotyledones are divided into three
divisions — Calyciferae, Corolliferae and Glumiflorae.
So in the latest system of Hutchinson, the
Dicotyledones consists of 83 orders and 349 families
and Monocotyledones consists of 29 orders and 69
families.

33. Merits and Demerits
Merits:
1. Hutchinson proposed the monophyletic origin of
angiosperms from some hypothetical
Proangiosperms having Bennettitalean
characteristics.
2. He made a valuable contribution in phylogenetic
classification by his careful and critical studies.
3. Monocots have been derived from Dicots.
4. According to him, the definitions of orders and
families are mostly precise, particularly in case of
subphylum Monocotyledones.

34. Demerits:
1. There is undue fragmentation of families.
2. Too much emphasis is laid on habit and habitat.
Thus, creation of Lignosae and Herbaceae is
thought to be a defect reflecting the Aristotelean
view.
3. The origin of angiosperms from Bennettitalean-like
ancestor is criticised by many, because the
anatomical structures of the early dicotyledons are
not tenable with such ancestry.

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