*sigh* for the non-biologists among you:
You can't cross cannabis with a plant that's not cannabis. No, not even hops (you can graft to hops, but not cross pollinate). I haven't heard of the glowing plant the OP was talking about, but plants that fluoresce under UV light have been created (as proof of concept, not for any 'real' purpose). First you need to isolate the GFP (green fluorescent protein) gene from jellyfish (or, more likely, just buy the damn stuff from a biochem lab supplier...it's very commonly used in research) and insert it into an agrobacterium through transformation . Then just breed your bacteria on selective media until you isolate the transgenic strain. Prepare a cell suspension and apply it to your plant tissue culture. With a bit of luck, some of the plant cells will take up the modified bacteria containing a plasmid with the GFP gene. Plants grown from these cells will all have the GFP gene, and will produce GFP (in theory) making them fluoresce under UV light. This trait would then be heritable (as far as i know).
Also, some of you people seem to think that strong enough fluorescence can drive photosynthesis...you're forgetting that the fluorescence is the result of UV absorption. There's no UV light in a dark room (or ridiculously minimal amounts), so the plant wouldn't glow. You could put in a UV light source, but then, why not just get a proper lamp? Also, the gene causes the plant to produce a protein, which glows (rather than just magically making the plant itself glow) and the production of anything requires energy; more energy than the GF proteins can emit through fluorescence. So, unless the laws of thermodynamics cease to apply to the plant in question, it is physically impossible for it to produce light that will drive photosynthesis, that will eventually produce light that keeps driving the photosynthesis, etc...