Detailed Classification of Kingdom Plantae

Kingdom plantae is further divided into various divisions based on various criteria. The first level of classification among plants depends on whether or not the plant body has well-differentiated, distinct components. The next level of classification is based on whether the differentiated plant body has special tissues (vascular tissues-the xylem and phloem) for transport of water and other substances within the plant body. Further classification of plants involves criteria, such as , ability to bear seeds and whether the seeds are enclosed within fruits.

1. 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 are Spirogyra, Ulothrix, Cladophora and Chara.
2. BRYOPHYTA:- These are called the amphibians of the plant kingdom. These 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 are moss (Funaria) and Marchantia.
3. PTERIDOPHYTA:-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. Some examples are Marsilea, Ferns and horse-tails. The thallophytes, the bryophytes and the pteridophytes have naked embryos that are called spores. The reproductive organs of plants in all these three groups are very inconspicuous, and they are therefore called ‘cryptogamae’, or ‘those with hidden reproductive organs’. On the other hand, plants with well-differentiated reproductive tissues that ultimately make seeds are called phanerogams. Seeds are the result of the reproductive process. They consist of the embryo along with stored food, which serves 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.
4. GYMNOSPERMS: This term is made from two Greek words: gymno-means naked and sperms- means seed. This plants of this group bear naked seeds and are usually perennial, evergreen and woody. Examples are pines and deodar.
5. ANGIOSPERMS: This word is made two Greek words: angio means covered and sperma-means seeds. The seeds develop inside an organ which is modified to become a fruit. These are also called flowering plants. Plants 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. Thus, cotyledons represent a bit of ore-designed plant in the seed. The angiosperms are divided into two groups on the basis of number of cotyledons present on the seed. Plants with seeds having a single cotyledons are called monocotyledons or monocots. Plants with seeds having two cotyledons are called dicots.

Fig: Classification of plants