Since Corn is wind pollinated, it's better to plant 4 or more short, side-by-side rows than 1 or 2 long rows. This will help pollination and ear development.
I planted my Glass Gem corn in 3 rows. about 15 inches apart. and planted the seeds 12 inches apart. I originally planted 2 rows of 17 seeds and 1 row of 10 seeds.
X X X X X X X X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X X X X X X X X
But then I had a little problem with some snail damage after the plants had been up about a week and it wiped out the red X's. I had 7 seeds left so I planted them to try to keep the big gap from being left. I put some organic snail bait out to try to keep the snails off the corn.
It didn't work as well as I had hoped it would and I wound up losing some more corn plants. It kinda left my corn looking like this:
X X X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X X
The 5 purple X's were 2 weeks behind in maturing and are where the "Pearl" kernels came from. And that one blue X was kinda left all by it's lonesome. it matured when the black X's did. But it was over there by itself. 7 feet away from the other stalks that were maturing when it did. And it affected it. It made some beautiful seeds, but that whole ear development thing didn't work out too well.
The top ear. That's the one from the plant by itself. Pretty kernels. Pitiful ear fill. The plant by itself didn't have much chance for any of the other plants to pollinate it. Those other plants were in the middle of a big pollination party. While that one was over by itself. Playing solitaire with a deck of 51 cards.