Velamen and spongy tissues are found in the epiphytic roots. These are hygroscopic and absorb water from the atmosphere. In adventitious roots when the rootlets are irregularly swollen, they are described as tuberous, e.g., Ipomoea batatas. In parasitic plants the parasitic or haustorial or sucking roots make a connection between the conducting systems of the two plants. In mangrove plants the tap roots become aerotropic andcome out of the soil. They are called pneumatophores or breathing roots.