Prepare two bags. This time, across the bottom of each bag, mark 4 arrows, one up, one down, one to the left and one to the right.
Place a bean above each arrow, so that the concave part of the seed is pointing in the direction of the arrow.
Hang the bag on the refrigerator (or on another vertical surface) and leave the other on a flat surface and observe.
Observe what happens with the seeds in the different bags.
Seeds rely on gravity to help them grow the "appropriate" way. When the bag is hanging vertically, the seeds will orient their roots so they all go down. Because the roots can't go "down" while the bag is laying flat, the roots in that bag will grow in whatever direction they can.