wrapping text in datagridview header columns

I have data grid view  and i want get the above done.  I have written the code like below.

  For Each col As DataGridViewColumn In dtg.Columns
            col.Width = dtg.Width / dtg.Columns.Count
 Next

 For Each col As DataGridViewColumn In dgv1.Columns
                col.DefaultCellStyle.WrapMode = DataGridViewTriState.True
  Next

dgv1.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.None
dgv1.AutoSizeRowsMode = DataGridViewAutoSizeRowsMode.AllCells

It is wrapping some of the columns correctly. but some col,  text is getting truncated. screen shot is enclosed.

Request early  help  to solve this issue.