Bentham and Hooker Classification

Bentham and Hooker Classification - Bentham and Hooker Classification

Introduction to Bentham and Hooker's classification of plants

It is a natural system of classification and is relies on significant characters of the plants. Yet today this system is being followed in United Kingdom (UK) and various other Commonwealth countries. It is also employed in several herbaria and botanical gardens all across the world. It is a well recognized and extensively accepted classification of seeded plants. It was planned through two English botanists George Bentham (from 1800- to 1884) and Sir Joseph Dalton Hooker (from 1817- to 1911).  The system of classification of them was introduced in 'Genera Plantarum' in three volumes and they had explained 97,205 species of seeded plants in 202 orders (now considered to as families). In classification of plants of Bentham and Hooker, the current day 'orders' were considered to as 'cohorts' and 'families' as 'orders'.

The seeded plants are categorized into 3 classes - Dicotyledon, Gymnosperm and Monocotyledon.

Class I Dicotyledon

Seeds of dicotyledonous plants consist of two cotyledons.  Leaves depict reticulate venation.  Flowers are tetramerous / pentamerous comprising four or five members in several floral whorls correspondingly. It involves three sub-categories - Gamopetalae, Polypetalae, and Monochlamydeae.

Sub-class I Polypetalae

Plants comprising flowers along with free petals come within polypetalae.  The flowers are with different calyx and corolla.  Polypetalae is additional divided into 3 series - Thalamiflorae, Disciflorae and Calyciflorae.

Series (i) Thalamiflorae

It involves plants comprising flowers with dome or conical thalamus. Ovary is superior.  Thalamiflorae involves 6 orders and 34 families.  The family Malvaceae is located in the order Malvales.

Series (ii) Disciflorae

It involves flowers comprising prominent disc shaped thalamus below the ovary. Ovary is superior. Disciflorae is separated into 4 orders and 23 families.

Series (iii) Calyciflorae

It involves plants comprising flowers with cup shaped thalamus.  Ovary is superior or inferior sometimes half inferior. Calyciflorae involves 5 orders and 27 families.

Sub-class 2. Gamopetalae

Plants comrising flowers with petals that are either partially or totally fused to one another are located under Gamopetalae.  The sepals and petals are different.  Gamopetalae is further categorized into three series - Inferae, Heteromerae and Bicarpellatae.

Series (i) Inferae

The flowers are epigynous and ovary is inferior. Inferae involves 3 orders and 9 families.

Series (ii) Heteromerae

The flowers are hypogynous and ovary is better with more than two carpels.  Heteromerae involves 3 orders and 12 families.

Series (iii) Bicarpellatae

The flowers are hypogynous and ovary is superior with two carpels only.   Bicarpellatae involves 4 orders  and 24 families. The family Solanaceae is positioned in the order Polemoniales.

Sub-class 3. Monochlamydeae

Plants comprising flowers with single whorl of perianth are positioned under Monochlamydeae. Flowers are incomplete. The sepals and petals are not differentiated and they are called perianth. Tepals are exists in two whorls. Occasionally both the wholrs are not present. Monochlamydeae   involves 8 series and 36 families.  The family Euphorbiaceae is positioned in the series Unisexuales.

Class II Gymnospermae

The members of Gymnospermae class have naked ovules or seeds. Ovary is not present and gymnospermae involves three families - Gnetaceae, Coniferae and  Cycadaceae.

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Flowchart: Outline of Bentham and Hooker's classificiation of plants

Class III  Monocotyledon

Seeds of monocotyledonous plants consist of only one cotyledon. Leaves depict parallel venation.  Flowers are trimerous comprising three members in several floral whorls.        The plants contain fibrous root system.  The Monocotyledon includes 7 series and 34 families.  The family Musaceae is positioned in the series Epigynae.

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