A special type of diffusion where water is absorbed by solids and colloids is called imbibitions. The volume of the substance absorbing water through imbibitions increases to a great extent. An example of this type of diffusion is absorption of water by dry wood and seeds. Imbibition is an important process as without it the seedlings cannot come out of the soil into the open. In imbibitionstoo the water transport occurs along the concentration gradient.