The HierarchicalDataTemplate doesn't show children - why not?

I'm trying to make it as simple as possible HierarchicalDataTemplate

to bind nested data with WPF TreeView

. For some reason, the children of my tree are not visible:

Here's the whole XAML:

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:src="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">
    <TreeView Name="ctTree">
        <TreeView.Resources>
            <HierarchicalDataTemplate DataType = "{x:Type src:MyClass}"
                                      ItemsSource = "{Binding Path=Children}">
                <TextBlock Text="{Binding Path=Name}"/>
            </HierarchicalDataTemplate>
        </TreeView.Resources>
    </TreeView>
</Window>

      

        
        
        
      

    

and heres all the C # behind this except apps and namespace:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        var collection = new ObservableCollection<MyClass>
        {
            new MyClass { Name = "parent one" },
            new MyClass { Name = "parent two" },
        };
        collection[0].Children.Add(new MyClass { Name = "child one" });
        collection[0].Children.Add(new MyClass { Name = "child two" });
        ctTree.ItemsSource = collection;
    }
}

class MyClass
{
    public string Name { get; set; }
    public ObservableCollection<MyClass> Children
        = new ObservableCollection<MyClass>();
}

      

        
        
        
      

    

Note that the data template does indeed apply to elements: the data is taken from the property Name

, and if the template was not applied, it will appear as "MyClass".

How can I show the children? I seem to be doing the same as all the examples on HierarchicalDataTemplate

.