This is the best known natural
system of classification put forwarded by two English botanists – George Bentham (1800 – 1884) and Sir Joseph Dalton Hooker (1817 -1911).
This system of classification was published in the book ‘Genera Plantarum’ (1862 -1883) which became the most popular
classification in European countries.
Bentham and Hooker divided all
Phanerogams or seed plants into Dicotyledons,
Gymnosperms and Monocotyledons. They discussed Dicotyledons
first, then Gymnosperms and finally Monocotyledons. There are altogether
202 families of Angiosperms in this system. They divided Dicotyledons into 3 sub-classes, sub-classes into 14 series, series into 25 cohorts (=order) and cohorts into 65 orders (=family).
Dicotyledons started with the family
Rannunculaceae and ended with Labiateae (Lamiaceae). They placed
Gymnosperms in between Dicotyledons and Monocotyledons. They divided
Monocotyledons into 7 series and series directly into 37 orders (family); i.e.,
cohorts (=orders) absent. The Gramineae
(Poaceae) is the ending family of monocotyledons.
A synoptic outline of Bentham and
Hooker system of classification is as follows –
Phanerogams or
Seed Plants
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Dicotyledons
(3 Sub-classes, 14 Series, 25 Orders
& 165 Families)
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Gymnosperms
(3 Families)
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Monocotyledons
(7 Series, 37 Families)
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Sub-Class I: Polypetalae
(3 series)
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Sub-Class II: Gamopetalae
(3 series)
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Sub-Class III: Monochlamydeae
(3 series)
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Family
I:
Gnetaceae
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Series 1: Microspermae
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Series 1: Thalamiflorae
(6 orders)
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Series 1:
Inferae
(3 orders)
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Series 1: Curvembryae
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Family
II:
Coniferae
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Series 2:
Epigynae
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Series 2: Disciflorae
(4 orders)
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Series 2: Heteromerae
(3 orders)
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Series 2: Multivulatae
aquatica
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Family
III:
Cycadaceae
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Series 3:
Coronarieae
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Series 3: Calyciflorae
(5 orders)
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Series 3: Bicarpellatae
(4 orders)
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Series 3: Multivulatae
terrestries
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Series 4:
Calycineae
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Series 4: Micrembryae
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Series 5:
Daphnales
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Series 6: Achlamydosporeae
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Series 7: Unisexuales
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Series 8:
Ordines
anomalis
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MERITS AND DEMERITS OF BENTHAM
& HOOKER’S SYSTEM OF CLASSIFICATION
MERITS
(a) It is the first great natural
system of classification.
(b) It is very easy to follow for
all practical purposes, and that is why Kew Herbarium and several other herbaria of the world, including India
are arranged according to this system.
(c) The description of families and
genera are very accurate.
(d) Ranales have been given
primitive position in this system. Recent taxonomic findings also indicate that Ranales are the most
primitive among angiosperms.
(e) In this system, the monocots are
derived from dicots. Several taxonomic findings also support this view.
(f) Placing Monochlamydeae at the
end of Dicots.
(g) Placing the unisexual monocot
families after bisexual families, i.e., Palmae and Araceae after Liliaceae.
(h) The series Glumaceae with extreme
reduced flowers and inflorescence, placed at the end of flowering plants.
DEMERITS
(a) The position of Gymnosperms
between Dicots and Monocots in this system is the foremost demerit. This arrangement is done
without considering the affinities among these groups.
(b) This system does not give any
idea about evolutionary history of any genus, family or order.
(c) In this system some closely
related families have been separated and placed under different orders (cohorts). In the same way numbers
of unrelated families have been grouped nearer.
(d) Advanced families such as
Orchidaceae have been considered primitive in this system by placing them in the beginning.
(e) Asteraceae is a highly advanced
family and placed in Inferae at the beginning of Gamopetalae.
(f) The position of series Apocarpae
is unsatisfactory due to its free and superior carpels.
(g) The entire arrangement of
monocots is unnatural and unphylogenetic in this system.
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