Can grass grow under glass in Minecraft?

Yes! Although you can not lay glass directly on top of the grass, you can put grass inside a glass structure and it will still grow. You may also grow grass by putting it on top of brick, sand, or even water. I will have to do some testing to see how close a block of glass may get to the grass without disrupting it. I believe it will grow green just fine whether it is a block or a block and a half distant.