poi 合并word中的表格的單元格時(shí)，跨行可以正確合并，跨列合并則失敗

poi 合并word中的表格的單元格時(shí)，跨行可以正確合并，跨列合并則失敗, 以下是合并列的代碼

 public  void mergeCellsHorizontal(XWPFTable table, int row, int fromCell, int toCell) {  
        for (int cellIndex = fromCell; cellIndex <= toCell; cellIndex++) {  
            XWPFTableCell cell = table.getRow(row).getCell(cellIndex);  
            if ( cellIndex == fromCell ) {  
                // The first merged cell is set with RESTART merge value  
                cell.getCTTc().addNewTcPr().addNewHMerge().setVal(STMerge.RESTART);  
            } else {  
                // Cells which join (merge) the first one, are set with CONTINUE  
                cell.getCTTc().addNewTcPr().addNewHMerge().setVal(STMerge.CONTINUE);  
            }  
        }  
    }  

有知道為什么的嗎？