This thread should have ended about 8 posts ago.
IT IS TAP ROOT DOWN, which is to say the little white tentril that peaks out of a germinated seed. But really, it doesn't matter one bit. Throw it in some soil (only about 1/4 of an inch deep, sometimes only lightly cover it with soil) and it will come. Water once it's in the cup, then put a small plastic baggie over the top for humidity, but make sure its not air tight. As soon as it sprouts, remove bags and let it grow for one more day before putting it under 12 hours of light. Then, on the second day, start the 18 hour light cycle.
Keep it going for 3 weeks, watering every 2 days at first, then usually longer towards the end of the period (4-6 days). Just remember, it's better for the soil to be dryer than saturated. At 3 weeks, add a small dosage of nutes 5-1-1 or something similar, and voila - your plants should be big enough to thrive. Also make sure if you start them in party cups, transplant them at 1-2 weeks to a bigger container as the roots grow extremely fast and it can really inhibit growth.
Have fun.