Charles Edwin Bessy: Bessey system of classification: History, Outline of Classification, Merit and Demerits of classification II With MCQ II Botany-Biology II Contribution of various botanist in taxonomy

Bessey system of classification

Type of system of classification: Phylogenetic system of classification 

History of classification

Charles E Bessey proposed a system of classification based on Benthon and Hooker system of classification named as Bessey"s system of classification.

He realigned Benthom and Hooker system according to evolutionary principles.

Bessey considered angiosperms to be evolved MONOPHYLETICALLY from cycadophyta .

His system is popularly known as Besseyan system, published under the title “The Phylogenetic Taxonomy of flowering plants”

The system proposed by him has never accepted and adopted to any great degree in the world.

BASIS AND OUTLINE OF THE CLASSIFICATION

Bessey gave the concept of Primitive flower called as Ranalian concept. 

The concept was based on the fact that the angiospermic flower arise from gymnospermic bisexual strobili having Microsporophyll on lower side and Megasporophyll on upper side .

The lower sporophyll by progressive sterilisation forms Perianth and the upper sporophyll forms the Stamen and Carpel. Primitive flower thus had numerous free perianth such as in Magnoliales (Magnoliaceae-Ranales).

He was the first to consider that the large size bisexual fewer with spiral arranged floral parts represents the primitive condition in angiosperms.

According to Bessey Ranales were the most primitive among angiosperms from which two branches were given out Monocots and Dicots.

He named Angiosperms as Anthophyta.

Classify Anthophyta into two classes

1.Alternifoliae        2. Oppositifoliae

The class Alternifoliae includes monocots and Oppositifoliae includes Dicots

The Alistimales among monocots and Ranales among Dicots are most primitive .

Each of the above class is divided into Sub Classes-Strobiloideae and Cotyloideae.

Alternifoliae :- This class is divided into two subclasses . The Subclass Strobiloideae includes 5 orders and 31 Families. The subclass Cotyloideae include 3 orders and 14 families

Oppositifoliae:-The class include two sublasses. Subclass Strobilloideae include three superorder's 13 orders.Subclass Cotyloideae includes two superorder and 10 orders.

The arrangement of various taxa in the groups is based on data available from Developmental, Histological and Morphological data.

The Bessey system is used more and more for writing of floras and monographs.

MERITS OF THE CLASSIFICATION

The gymnosperms which are placed between monocots and dicots have been dropped.

The system gains support due to the position of Ranales as primitive order.

The concept of primitive flower is also acceptable.

Monochlamydae have been abolished.

The family with inferior ovary follow family with superior ovary.

Ordere Alistimales among monocot and Ranales among dicots are placed at starting point as they are considered as primitive.

Order Compositae and Asterae placed at last as they are advanced.

DEMERITS OF THE CLASSIFICATION

The gymnosperms which are placed betwen monocots and dicots have been dropped.

The system gains support due to the position of Ranales as primitive order.

The concept of primitive flower is also acceptable.

Monochlamydae have been abolished.

The family with inferior ovary follow family with superior ovary.

Ordere Alistimales among monocot and Ranales among dicots are placed at starting point as they are considered as primitive.

Order Compositae and Asterae placed at last as they are advanced .