1. Robert Whittaker proposed the five kingdom classification system for living organisms in 1959. This system places all plants in the kingdom Plantae.
2. In 1883, botanist Eichler classified the kingdom Plantae into two subkingdoms: Cryptogams and Phanerogams.
3. Cryptogams reproduce by spores without flowers or seeds and include algae, lichens, mosses and ferns. Thallophyta and Bryophyta are two divisions of Cryptogams.