Tag not work in children gameobject

In Unity 4.5.x I have one parent GameObject set "Untagged" and same GameObject tagged "TR".
If the player collide with one GameObject "TR" the collider.tag is always "Untagged" such us the parent's gameobject tag. Why ?

thanks

 

I found that in the answers.
Does that help?
http://answers.unity3d.com/questions/346789/colliding-with-the-tag-of-a-child-object.html