Major Groups of Plants
The plant kingdom is divided into cryptogams, in which there are no true flowers producing seed, and phanerogams, in which the plants develop flowers or flower-like structures where seeds are produced.
Cryptogams are again subdivided into Thallophyta, Bryophyta and Pteridophyta. Thallophyta are plants that possess a thallus or plant-body that is not differentiated into stem and leaves. To this group belong the algae, diatoms, fungi, bacteria and lichens.
Bryophyta include the liverworts and true mosses that are distinguished from Thallophyta by the possession of female reproductive organs, known as archegonia, and also by the fact that the plant-body is not frequently differentiated into stem and leaves.
Pteridophyta are fern-like plants. These plants possess vascular strands and there is often a marked differentiation into stem and leaves (Alsophila), the latter often being very large and much divided. The female reproductive organs, the archegonia, are similar to those developed in Bryophyta. In addition to the true ferns this group also includes the horsetails (Equisetum spp.) and the clubmosses (Lycopodium spp.).
Phanerogams include all higher plants.
Example : all present-day groups that exhibit the highest development and that are usually referred to as Spermatophyta.
This group is again subdivided into two phyla, namely: gymnosperms and angiosperms.
In gymnosperms, the male and female reproductive organs are not contained in the same flower and the ovules are borne naked on the carpels, which usually take the form of scales. (This phylum consists of seven major family groups including Coniferales.) On the other hand, in angiosperms the ovules are contained in a closed vessel, the ovary, and the male and female elements are usually, but not always, associated in the same flower. Flowering plants come under this category
Angiospermae are divided into two subphyla: monocotyledons and dicotyledons. Monocotyledons consist of six major groups of families, including Palmales and Graminales. The dicotyledons consist of Lignosae or woody plants (with some 50 groups of families) and Herbaceae or non-woody plants (with 17 groups of families).