<form action="" method="POST">
       <input type="hidden" value="<?php  csrf_field();;?>" id="token">
       <input type="text"  name="txtcorreo" id="idtxtcorreo" value="">
       <input type="submit" name="Login" value="Identificarse"  id="Registro" >
   </form>

$("#Registro").click(function () {
            var dato = $("#idtxtcorreo").val();
            var route = "http://localhost/MacAltia/public/Login";
            var token =$("#token").val();

            $.ajax({
                url: route,
                headers:{'X-CSRF-TOKEN'}
                type: 'POST',
                dataType: 'json',
                data: {genre: dato}
            })
        });

Route::post('Login', "ControladorSistema@Login");

public function Login(Request $request) {

         if($request->ajax()){
             echo "hay ajax";
         }else{
             echo "no hay";
         }
    }