How do I call method of Form1 from Form2

namespace WindowsFormsApplication
{
    public partial class Form1 : Form
    {
        internal static Form2 form2;
        internal static Form1 form1;

        public Form1()
        {
            InitializeComponent();
            form1 = this;//refering to the current Form1
        }

        private void buttonShowForm2_Click(object sender, EventArgs e)
        {
            form2 = new Form2();
            form2.Show();
        }

        public void ShowText()//the method which I want to call
        {
            textBoxInForm1.Text = "Method Called From Another Form";
        }
    }
}

namespace WindowsFormsApplication
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        private void buttonCallMethod_Click(object sender, EventArgs e)
        {
            Form1.form1.ShowText();//the method defined in Form1
            this.Close();
        }
    }
}

public partial class Form2 : Form
{
  Form1 form1;
  public Form2(Form1 form1)
  {
      this.form1 = form1;
      //...
  }
  private void buttonCallMethod_Click(object sender, EventArgs e)
  {
      form1.ShowText();//the method defined in Form1
      //...
  }
  //...