This explanation, like so many others relating to Tuth-Shena and Horus, might seem specious were it not for the other, associated plants that have psychoactive properties: the central flower and leaf of Nymphaea caerulea; at the foot of Horus, the unguent jar wrapped with the narcotic water lily bud; the strand of grapes and their leaves hanging from the opposite side of the supporting pedestal upon which offerings rest; the four repeated presentations of a cleft water lily leaf in the series glyphs at the right-hand margin. It is the realm of the dead, evidenced by the resin cone on the head of Tuth-Shena. The light is the light of Horus, realized in the psychoactive flowers of Datura which "illuminate" Tuth-Shena in allegorical fashion. It is the power of Horus before which she throws up her hands in awe. Vitis, Nymphaea, and Datura are the intoxicating elements portrayed in this scene of shamanic manifestation.
It is perhaps by coincidence that the frequency of portrayal of psychogenic plants is correlated with the level of development of ancient civilizations, but I do not think so. A shamanic caste appears and, subsequently, there is further shamanic stratification, the adjuncts to these priestly offices--that is to say, psychoactive plants--increase. The length of the associated rituals is progressively increased, and the litanies or magical incantations become hypertrophied. We can see the same thing among the Maya. It parallels the complexity of medicine and medicinal practives, for all these are inseparable at a certain level. They are manifestations of belief systems that enhanced by altered states of consciousness.