JavaFX 2.0 :: How Does Fill Mode Work In GridPane Column Constraints

The following code uses a column constraint to specify that a column of labels should extend horizontally in their cell but they don't as you can see by looking at their border. My mistake or a bug?

import javafx.application.Application;
import javafx.geometry.HPos;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;

[Code] ....