The Bentham and Hooker’s system of classification | Merits and Demerits | Plant taxonomy

The Bentham and Hooker’s system of classification :

The most accepted natural system of classification was proposed by Bentham and Hooker in their Genera plantarum published during July 1862 and April 1883. Bentham, a self-trained British botanist, and Hooker, the director of the Royal Botanic Gardens, Kew (England), described all known genera of seed plants in three volumes of their Genera Plantarum, published in Latin.

      Bentham and Hooker’s system of classification is still used and followed in several herbaria of the world. In most of the Indian herbaria too, the plants are arranged according to this system of classification. It is supposed to be the best system for the students to identify plants in laboratories. This is so because Bentham and Hooker prepared the generic descriptions of the plants from their own observations and not by copying from the available literature.

     In all, they described 97,205 species belonging to 7,569 genera of 200 families of flowering plants in three volumes of Genera Plantarum .

Number of orders, genera, and families described by Bentham and Hooker

Groups	Orders       ( Families )	Genera	Species
Dicotyledons (a) Polypetalae (b) Gamopetalae (c) Monochlamydeae	82 45 36	2,610 2,619 801	31,874 34,556 11,784
Gymnosperms	3	44	415
Monocotyledons	34	1,495	18,576
Total	200	7,569	97,205

Bentham and Hooker divided all Phanerogams or seed plants into Dicotyledons, Gymnosperms, and Monocotyledons.

(A) Dicotyledons

1. Polypetalae (Corolla of separate petals)

2. Gamopetalae (Petals of the corolla are partially or completely fused)

3. Monochlamydeae (Petals of absent)

(B) Gymnospermae (naked-seeded plants): Gneraceae, Coniferae, Cycadaceae.

(C) Monocotyledons (Parallel venation; one cotyledon; trimerous flowers).

Merits of the system of Bentham and Hooker :

1. It is the first great natural system of classification.

2. 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.

3. This system was never planned by Bentham and Hooker on the basis of Phylogeny, although the story of organic evolution was already announced by Darwin and Wallace in 1859, So this system should not be criticized on the basis of Phylogeny.

4. Ranales have been given a primitive position in this system. Recent taxonomic findings also indicate that Ranales are the most primitive living angiosperms.

5. In this system, the monocots are derived from the dicots. Several recent taxonomic findings support this view.

Demerits of the system of Bentham and Hooker :

1. The position of gymnosperm in between dicots and monocots in this system is its foremost demerit. This arrangement is made without considering the affinities among these groups.

2. Several important floral characters have been neglected in this system.

3. Advanced families such as Orchidaceae, have been considered primitive in this system by placing them in the beginning.

4. The entire arrangement of monocots is unnatural and unphylogenetic in this system.


                        

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