Azolla forms red coloured bloom in ditches and ponds. It is found floating freely on the surface of water. Common Indian species is A. pinnata. Another species A. filiculoides is also known to occur frequently while the third species A. imbricata is found mostly in Eastern Himalayas.
The two Indian species, Marsilea minuta and M. quadrifolia, are commonly found growing either in shallow water or on moist banks of ponds and ditches. They grow either completely submerged or partially or entirely out of water in damp and wet places.
Pteridium is cosmopolitan. It is widely distributed along the entire Himalayan tract. It grows particularly well at altitudes between 1,000 to 3,000 meters. P. aquilinum is found on forest floors, mountain slopes, open grasslands, etc.
NEPHROLEPIS (SWORD FERN) is commonly found in tropics, but a few species like Nephrolepis acuta, N. tube rosa, etc. are also grown as ornamentals.
Adiantum is very common in hills, lower slopes of the hills and in the plains. In hills it is commonly seen in dense evergreen forests and also on limestone rocks.
Equisetum debile which is common in India grows abundantly along the banks of rivers, in sandy soil and on the woods along the river. Another common species, E. arvense, grows in grasslands
About 58 species of Selaginella have so far been reported from India. Many Indian species are found growing in western and eastern Himalayas and the hills of South India on damp shady sides. A few species are xerophytic. S. oregana is epiphyte on trunks and branches of moss covered trees in the forests.
The genus Lycopodium is divided in to 2 sub-generaUrostachya and the Rhopalostachya.
Only two species of Psilotum viz. P. nudum (=P. triquetrum) and P. jlaccidum (=P. complanatum) are known. These are widespread in tropical and subtropical regions of both the hemispheres.