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Bentham and Hooker’s System of Classification

Bentham and Hooker’s System of Classification

George Bentham and Sir Joseph Dalton Hooker developed a system of classification. They published thier work in Latin, which was entitled “Genera Plantarum”.This system of classification is a natural non-phylogenetic system which is a slight modification of de-Condolle’s system of classification.In this system, the flowering plants are divided on the basis of simple superficial characters neglectinng some floral characters.In this system the position of Gymnosperms is anamalous i.e. in between dicotyledons and monocotyledons.Arboreous and herbaceous habits are to be neglected in this system.The bentham and Hooker’s sysem of classification is as follows:

The plant kingdom is divided into two main divisions;

Division Angiospermae

Division Gymnospermae

  1.  Division Angiospermae:

This division includes spermatophytes(seed plants).In seed plants, there are total 3 sub-classes, 21 series, 25 cohorts and 202 orders.These are to be classified into following classes,

Class Dicotyledons

Class Monocotyledons

  1.  Class Dicotyledons:

The dicotyledons are the plants which have seeds containing two cotyledons and are to be divided into three sub-classes;

Sub-class Polypetalae

Sub-class Gamopetalae

Sub-class Monochlamydeae

  1.  Sub-class Polypetalae:

This subclass include all the plants with corolla of separate petals.It include 3 series;

Series 1: Thalamiflorae

stamens are hypogynous

include 6 cohorts

33 orders

Series 2: Disciflorae

hypogynous disc is present

stamens are definite

stamens are twice the number of petals

4 cohorts

23 orders

Series 3: Calyciflorae

sepals are united

stamens are epigynous

5 cohorts

27 orders

  1.  Sub-class Gamopetalae:

It include plants having corolla with united petals.It is divided into 3 series;

Series 1: Inferae

stamens are as many as petals and altering with them

ovary is inferior

3 cohorts

9 orders

Series 2: Heteromerae

stamens are as many as corolla lobes

carpels are more than 2

ovary is superior or inferior

3 cohorts

9 orders

Series 3: Bicarpellatae

stamens are as many as corolla lobes

ovary is bicarpellary

ovary is superior

iii.  Sub-class Monochlamydeae:

It include plants having perianth 1-2 seriate and mostly sepaloid.It is divided into 8 series;

Series 1: Curvyembryeae

seeds are with endosperm

embryo is curved

ovary is one ovuled

7 orders

Series 2: Multiovulatae aquaticae

most are immersed aquatc herbs

ovary is syncarpous

ovary is many ovuled

single order

Series 3: Multiovulatae terrestris

most are terrestrial herbs

ovary is syncarpous

many ovules

3 orders

Series 4: Microembrayeae

carpels are 1-2 ovuled

4 orders

Series 5: Daphnales

ovary is monocarpellary

3 orders

Series 6: Achlamydosporeae

ovary is unilocular

3 orders

Series 7: Unisexuals

flowers are unisexuals

9 orders

Series 8: Ordines anomali

4 natural orders

  1.  Class Monocotyledons:

This class include seed plants with one cotyledon.It is divided into 7 series;

Series 1: Microspermae

Series 2: Epigynae

Series 3: Corenarieae

Series 4: Calycinae

Series 5: Nudiflorae

Series 6: Apocarpae

Series 7: Glumaceae

  1.  Division Gymnosperms:

This division is placed in between dicotyledons and monocotyledons and is further classified into three orders:

  1.  Gnetaceae
  2.  Coniferae

iii.  Cycadaceae

Characteristics of Division Gymnosperms:

The gymnosperms are treated as the third taxon, which is collateral with and placed between dicotyledons and monocotyledons.Various genera were grouped under different orders and different orders were plced under many “cohorts” were based on all similarities and differences.

Certain orders which could not be satisfactorily placed in any cohort, which were treated as anomalous orders i.e. Ordines anomali.

Merits Of Bentham and hooker classification:

It is very natural and easily workable

This classification provides the basis for arrangement of plants in many important herbaria of commonwealth countries

In this system, main emphasis is to be given on the contrast between free and united petals.

An important feature of this system is addition of Disciflorae.

The arrangement of certain groups is on the basis of aquatic and terrestrial characters.

In class monocotyledons, the emphasis is given on the ovary and perianth characteristics.

Demerits:

The basis of this system does not include phylogenetic relationships

The position of gymnosperms is not satisfactory

There are many orders in class monochlamydeae having biseriate perianth like in all orders of polypetalae

Orchidaceae is not placed at satisfactory position

The origin of angiosperms was not established.

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