Thallophyta, Bryophyta, Pteridophyta, Gymnosperms and Angiosperms
The first level of classification among plants depends on whether the plant body has welldifferentiated, 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.
- 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, Ulva and Chara.
- 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 are moss (Funaria) and Marchantia.
- 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 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 well differentiated
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:
- 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 are pines and deodar
- 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.
- Monocotyledonous / monocots - Plants with seeds having a single cotyledon.
- Dicots - Plants with seeds having two cotyledons.