Problems with running phpmailer from ajax

I would like to tell you that I want to send a form by ajax and that this data is obtained to execute the PHPMailer function. The problem is that from the file send _mensaje.php I get the following errors:

  

Undefined index serial in ....   Undefined index marks in ....

And so on with the rest of the variables.

The codes are the following:

Form

<form class="contact-form row" id="form-reportarbici">
                        <div class="col-md-4">
                            <label></label>
                            <input type="text" class="form-control" placeholder="Serial" id="serial" required>
                        </div>
                        <div class="col-md-4">
                            <label></label>
                            <input type="text" class="form-control" placeholder="Marca" id="marca" required>
                        </div><br>
                        Cuéntale dónde la encontraste... <br>
                        <div class="col-md-4">
                            <label></label>
                            <input type="text" class="form-control" placeholder="Localidad" id="localidad" required>
                        </div>
                        <div class="col-md-4">
                            <label></label>
                            <input type="text" class="form-control" placeholder="Barrio" id="barrio" required>
                        </div>
                        <div class="col-md-4">
                            <label></label>
                            <input type="text" class="form-control" placeholder="Direccion (opcional)" id="direccion">
                        </div>
                        <div class="col-md-12">
                            <label></label>
                            <textarea class="form-control" rows="9" placeholder="Mensaje adicional (opcional)" id="mensaje"></textarea>
                        </div>
                        <div class="col-md-4 col-md-offset-4">
                            <label></label>
                            <button type="submit" data-toggle="" data-target="#" class="btn btn-primary btn-block btn-lg" id="btn_reportar">Enviar <i class="ion-android-arrow-forward"></i></button>
                        </div>
                    </form>

Send by Ajax:

 $(document).ready(function(){

       $('#form-reportarbici').submit(reportar)

        function reportar(evento){

        evento.preventDefault();
        alert("enviando");

        var datos =  new FormData($('#form-reportarbici')[0])

        $.ajax({
            url: 'enviar_mensaje.php',
            type: 'POST',
            data: datos,
            contentType: false,
            processData: false,

            success: function(datos){
                alert(datos);
            }

        })

        }

 });

Reception in PHP:

date_default_timezone_set('Etc/UTC');
require 'PHPMailer/PHPMailerAutoload.php';

require ('conexion.php');

    $nombre = "";
    $link = "";

    $serial=    $_POST['serial'];
    $marca=     $_POST['marca'];
    $localidad= $_POST['localidad'];
    $barrio=    $_POST['barrio'];
    $direccion= $_POST['direccion'];
    $mensaje= $_POST['mensaje'];

Maybe it's good to say the jquery bookstore ... Although this one has worked quite well for me.

 <script src="http://code.jquery.com/jquery-latest.min.js"></script>