BOTANY Higher Secondary Second Year - Textbooks Online

1. TAXONOMY OF ANGIOSPERMS
Taxonomy is concerned with the laws governing the classification of
plants. The term taxonomy includes two Greek words taxis – arrangement
and nomos– laws. Plant taxonomy is otherwise known as systematic
botany. Classification, identification, description and naming the plants
are the bases of plant taxonomy. The taxonomic knowledge about the
plants is based on their form and structure. The knowledge gained through
taxonomy is useful in the fields of medicine, agriculture, forestry, etc.
The ultimate aim of classification is to arrange plants in an orderly
sequence based upon their similarities. The closely related plants are kept
within a group and unrelated plants are kept far apart in separate groups.
The other aim of classification is to establish phylogenetic relationships
among the different groups of plants. The plants that are closely related
show more similarities than differences.
The earliest systems of classification were simple and based on one or
few characters. They gave importance to vegetative characters. The later
systems of classification gave more importance to floral characters because
floral characters are more stable and permanent.
1.1. Types of classification
The different types of classification proposed by earlier taxonomists
can be broadly categorized into three systems– artificial, natural and
phylogenetic.
Artificial system
It was based on one or at most only a few superficial characters. In
1753, Carolus Linnaeus of Sweden published his book “ Species
Plantarum” wherein he described 7,300 species. He divided the plants
into 24 classes based on number, union, length and certain other characters
of stamens. Hence, this system is also known as sexual system of
classification. In those days, it was an important over other systems of
classification. The importance of floral characters was felt by Linnaeus
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