Epiphytic roots are also called hygroscopic roots. Epiphytes bear three types of roots clinging, absorbing and hygroscopic aerial. These roots develop in some orchids which grow as epiphytes upon the trunks or branches of trees. They hang freely in the air and absorb atmospheric moisture with the help of special sponge like tissue called velamen. Velamen is modification of epidermis e. g. Vanda, Dendrobium etc.