Plant Kingdom | Classification of Plants

The first level of classification among plants depends on whether the plant body has well differentiated, distinct parts. The next level of classification is based on whether the differentiated plant body has special tissues for the transport of water and other substances. Further classification looks at the ability to bear seeds and whether the seeds are enclosed within fruits.

 

a) Thallophyta: Plants that do not have well-differentiated body design fall in this group. The plants in this group are commonly called algae. These plants are predominantly aquatic. 
Examples:  Spirogyra, Ulothrix, Cladophora, Ulva and Chara

b) Bryophyta: These are called the amphibians of the plant kingdom. The plant body is commonly differentiated to form stem and leaf-like structures. However, there is no specialised tissue for the conduction of water and other substances from one part of the plant body to another. 
Examples: Moss (Funaria) and Marchantia

 
c) Pteridophya  :In this group, the plant body is differentiated into roots, stem and leaves and has specialised tissue for the conduction of water and other substances from one part of the plant body to another. 
Examples: Marsilea, ferns and horse-tails

The reproductive organs of plants in all these three groups are very inconspicuous, and they are therefore called ‘cryptogams’, or ‘those with hidden reproductive organs’. On the other hand, plants with welldifferentiated reproductive parts that ultimately make seeds are called phanerogams. Seeds are the result of sexual reproduction process. They consist of the embryo along with stored food, which assists for the initial growth of the embryo during germination. This group is further classified, based on whether the seeds are naked or
enclosed in fruits, giving us two groups: gymnosperms and angiosperms.

d) Gymnosperm : This term is derived from two Greek words: gymno– means naked and sperma– means seed. The plants of this group bear naked seeds and are usually perennial, evergreen and woody. 
Examples:  Pines and Deodar

e) Angiosperms:  This word is made from two Greek words: angio means covered and sperma– means seed. These are also called flowering plants. The seeds develop inside an ovary which is modified to become a fruit. Plant embryos in seeds have structures called cotyledons. Cotyledons are called ‘seed leaves’ because in many instances they emerge and become green when the seed germinates. 

The angiosperms are divided into two groups on the basis of the number of cotyledons present in the seed. Plants with seeds having a single cotyledon are called monocotyledonous or monocots. Plants with seeds having two cotyledons are called dicots