The above diagram explores one more aspect of the sexual symbolism on the Tree of Life, exploring some the often-ignored representations of the Sephiroth. The most obviously sexual Sephirah is, of course, Yesod. When the Tree is assigned to parts of the body, Yesod represents the reproductive organs. This can also be seen via its role as the watery lunar sphere, representing the reproductive fluids, as well as the menstrual cycle of women, obviously connected to their reproductive organ.
But these are not the only sexual Sephiroth, for Hod and Netzach are sometimes depicted as the testicles (more often, however, as the legs), pumping the sperm into the phallus of Yesod. And the energy that goes behind this, the ultimately primordial "drive", comes from Chokmah and Binah, their divine counterparts, pushing energy down into Tiphareth, which distributes it to the "testicles" of Hod and Netzach, then to Yesod, and lastly into the womb of Malkuth.
This is but one example of the various arrays of sexual symbolism in the Qabalah, but it is one that is rarely seen, explored, or understood. Sex is but another warehouse of myth that the ancient Qabalists utilised in their attempts to hint at the majesty of God.