Classification: relative merits and demerits of classification - Bentham and Hooker

Classification: relative merits and demerits of classification - Bentham and Hooker:- Two English botanists, Bentham and Hooker gave the most well-known natural system of classification for seed plants. Their classification was published in 3 volume work Genera Plantarum (1862-83). In this article, we will be further discussing the merits and demerits of the Bentham and Hooker Classification.

System of Classification:-

> Total families considered in the Bentham and Hooker classification were 202 including 7569 genera further including 97,205 species. 

> This classification was not just a simple compilation of facts rather, it was based on personal studies of specimens. 

> Many herbaria of the world have specimens arranged in accordance with this system of classification. 

> In this system of classification, seed plants ie. phanerogams were divided into Dicotyledons, Gymnosperms and Monocotyledons. 

> Bentham and Hooker further classified the Dicotyledons into 3 classes namely Polypetalae, Gamopetalae and Monochlamydeae. 

> These subclasses were further subdivided into series, cohorts (orders) and natural orders (now called families). 

Merits and Demerits of Bentham and Hooker classification:-

Merits:- Advantages of Bentham and Hooker classification are discussed as follows:

i. The system proves to be of excellent practical application in the identification of unknown plant samples.

ii. In the herbaria of many countries especially in the case of Britain and India, specimens are arranged in accordance with this system of classification.

iii. It is not just a mere assembly of facts rather it is based on a careful examination of actual specimens. 

iv. Gymnosperms are not placed amongst dicotyledons rather they are placed in a separate independent group.

v. Despite, not being a phylogenetic system, Ranales are arranged at the beginning of dicots which is accepted by most present-day systematists.

vi. Most present-day authors approve of Dicotyledons being placed before Monocotyledons which is the case in the Bentham and Hooker classification.

vii. The descriptions provided for various families are very accurate and the keys are also very helpful in the identification process.

viii. This system is based on natural affinities ie. morphological characteristics and hence, they are easily observable.

ix. Heteromerae is rightly placed before Bicarpellatae.

x. The grouping is based on a combination of characters and not just any single character.

Demerits:- Disadvantages of Bentham and Hooker classification are discussed as follows-

i. It is not a phylogenetic system of classification. 

ii. Gymnosperms are incorrectly placed between dicots and monocots. Their proper position is before the dicotyledons since they form a separate group from angiosperms.

iii. Present-day authors think of Liliaceae and Amaryllidaceae as closely related families and often include them in the same order. However, in the case of Bentham and Hooker classification, they are placed in separate series. Liliaceae is included under Coronarieae and Amaryllidaceae is included under Epigynae.

iv. Monochlamydeae is an unnatural assemblage and the formation of this group has led to the separation of many closely related families. Closely related families namely Caryophyllaceae, Illecebraceae and Chenopodiaceae are placed in same order by modern day taxonomists. However, in this system of classification,  Caryophyllaceae is placed in Polypetalae and the other two in Monochlamydeae.

v. Unisexuales is a loose assemblage of diverse families which have only one common character that is unisexual flowers.