How have instructions been interpreted in the context of marijuana possession cases?

"It may be possible to argue that taking the instructions as a whole, they were sufficient to have informed the jury in a general roundabout way that before defendant could be convicted of ... the possession of marijuana the evidence must show his knowledge of the presence of said property in his box; but since knowledge, in that limited sense, is an essential element of the offense, he was entitled under the circumstances to a specific instruction such as the requested instruction, to clarify the situation." (People v. Gory, supra, 28 Cal.2d 450, 458-459, 170 P.2d 433.)