Plantae Kingdom

                Plants, also called green plants (Viridiplantae in Latin), are living multicellular organisms of the kingdom Plantae. They form a clade that includes the flowering plants, conifers and other gymnosperms, ferns, clubmosses, hornworts, liverworts and mosses, as well as, depending on definition, the green algae. Plants exclude the red and brown seaweeds such as kelp, the fungi and bacteria.
                  Green plants have cell walls with cellulose and characteristically obtain most of their energy from sunlight via photosynthesis using chlorophyll contained in chloroplasts, which gives them their green color. Some plants are parasitic and have lost the ability to produce normal amounts of chlorophyll or to photosynthesize. Plants are also characterized by sexual reproduction, modular and indeterminate growth, and an alternation of generations, although asexual reproduction is common, and some plants bloom only once while others bear only one bloom.

Algae
               Algae comprise several different groups of organisms which produce energy through photosynthesis and for that reason have been included in the plant kingdom in the past. Most conspicuous among the algae are the seaweeds, multicellular algae that may roughly resemble land plants, but are classified among the brown, red and green algae. Each of these algal groups also includes various microscopic and single-celled organisms. There is good evidence that some of these algal groups arose independently from separate non-photosynthetic ancestors, with the result that many groups of algae are no longer classified within the plant kingdo.
    Green algae from Ernst Haeckel's Kunstformen der Natur, 1904. 

Fungi
                 The classification of fungi has been controversial until quite recently in the history of biology. Linnaeus' original classification placed the fungi within the Plantae, since they were unquestionably not animals or minerals and these were the only other alternatives. With later developments in microbiology, in the 19th century Ernst Haeckel felt that another kingdom was required to classify newly discovered micro-organisms. The introduction of the new kingdom Protista in addition to Plantae and Animalia, led to uncertainty as to whether fungi truly were best placed in the Plantae or whether they ought to be reclassified as protists. Haeckel himself found it difficult to decide and it was not until 1969 that a solution was found whereby Robert Whittaker proposed the creation of the kingdom Fungi. Molecular evidence has since shown that the last common ancestor (concestor) of the Fungi was probably more similar to that of the Animalia than of any other kingdom, including the Plantae.

  The evolution of plants has resulted in increasing levels of complexity, from the earliest algal mats, through bryophytes, lycopods, ferns to the complex gymnosperms and angiosperms of today. The groups which appeared earlier continue to thrive, especially in the environments in which they evolved.