What's the law on inheritance, if a man owned the land before he married, they then had two children in which one child proceeded him in death but had a son? There is no will. I have been told that in the state of Louisiana that the land should have been divided between the mans wife, son and the heir of his deceased son is this true?

Actually, Louisiana has some very particular rules about inheritance, since they are based on the Napoleonic code, not the British Common Law.

And, a quick Google seems to show that, in this case, the spouse has no claim on the property. It's separate property, not community, and thus goes to the children and the children's heirs.