Eichler divided plant kingdom into two sub- kingdoms cryptogamae and phanerogamae. All plants without flowers and seeds are included in the sub kingdom cryptogamae whereas phanerogamae includes plants which bear flowers and seeds. Cryptogams are further classified into three divisions: Thallophyta, Bryophyta and Pteridophyta. Spore bearing plants such as mosses and ferns belong to cryptogams because instead of reproducing by flowers and seeds, they reproduce by means of spores. (Ref. to Fig.