Krishna uses the Ashwatta tree (Banyan) as a symbol of the Universe. [see Isis, I, 153; S.D., I, pp. 406, 536, 549] He declares that it grows inverted, with its roots above and its branches below, ramifying among mankind.
The many "leaves" are the Vedas (Holy Scriptures and Rules—see Gita, p. 108) of which Krishna declares himself, to be the sole interpreter.
"Its branches grow out of the three qualities [Sattva - Rajas - Tamas, see Gita, Chapter 14]...with the objects of sense as the lesser shoots, spread forth, some above and some below in the regions of mankind are the connecting bonds of action" [karma]. (Gita, p. 105)
As a symbol, the eternal, "Mundane Tree," cannot be fully understood, unless we see that it is the mind aspect of Nature. Because of its connection with desire, this latter has to be destroyed, "hewn down with the strong axe of dispassion." (Gita, p. 105) Following this, the Primeval Spirit is to be sought for: "from which floweth the never-ending stream of conditioned existence."
Dispassion is achieved by those who:
"...are free from pride of self and whose discrimination is perfected, who have prevailed over the fault of attachment to action, who are constantly employed in devotion to meditation upon the Supreme Spirit, who have renounced desire and are free from the influence of the opposites known as pleasure and pain, are undeluded..." They proceed "to that place which endureth forever..." It is Krishna's Supreme Abode. (Gita, p. 106)
Expanding further Krishna declares:
"It is even a portion of myself which, having assumed life in this world of conditioned existence, draweth together the five senses and the mind in order that it may obtain a body and may leave it again. And those are carried by the Sovereign Lord to and from whatever body he enters or quits, even as the breeze bears the fragrance from the flower."
"Presiding over the eye, the ear, the touch, the taste, and the power of smelling, and also over the mind, he experienceth the objects of sense."
"The deluded do not see the Spirit when it quitteth or remains in the body, nor when, moved by the [three] qualities it has experience in the world. But those who have the eye of wisdom perceive it, and devotees who industriously strive to do so, see it dwelling in their own hearts; whilst those who have not overcome themselves, who are devoid of discrimination, see it not, even though they strive thereafter...I am in the hearts of all men, and from me come memory, knowledge, and also the loss of both..." (Gita, pp. 106-7)
Two kinds of beings are in the world: the divisible, which are "all things and the creatures;" and the indivisible, which is the Supreme Spirit—Paramatma—"which permeates and sustains the three worlds...He who...knoweth me thus as the Supreme Spirit, knoweth all things." (Gita, p. 108)