Bhagavad-gītā 15.2

The description of the banyan tree is further explained here. Its branches are spread in all directions. In the lower parts, there are variegated manifestations of living entities, such as human beings, animals, horses, cows, dogs, cats, etc. These are situated on the lower parts of the branches, whereas on the upper parts are higher forms of living entities: the demigods, Gandharvas (fairies), and many other higher species of life. As a tree is nourished by water, so this tree is nourished by the three modes of material nature. Sometimes we find that a tract of land is barren for want of sufficient water, and sometimes a tract is very green; similarly, where the modes of material nature are proportionately greater in quantity, the different species of life are manifested in that proportion.

The twigs of the tree are considered to be the sense objects. By development of the different modes of nature, we develop different senses, and, by the senses, we enjoy different varieties of sense objects. The source of the senses—the ears, the nose, eyes, etc.—is considered to be the upper twigs, tuned to the enjoyment of different sense objects. The leaves are sound, form, touch-the sense objects. The roots, which are subsidiary, are the by-products of different varieties of suffering and sense enjoyment. Thus we develop attachment and aversion. The tendencies toward piety and impiety are considered to be the secondary roots, spreading in all directions. The real root is from Brahmaloka, and the other roots are in the human planetary systems. After one enjoys the results of virtuous activities in the upper planetary systems, he comes down to this earth and renews his karma or fruitive activities for promotion. This planet of human beings is considered the field of activities.