Laravel - onDelete("cascade") does not work

I have an Laravel 4 app with polls and different options or choices to vote. The problem is that when I destroy a poll, the options are not deleted from the database.

These are my main migrations:

Polls:

private $table = 'polls';

public function down() {
    Schema::dropIfExists($this->table);
}

public function up() {
    Schema::create($this->table, function(Blueprint $table) {

        $table->increments('id');
        $table->string( 'owner'      )->unsigned();
        $table->foreign('owner'      )->references('id')->on('users')->onDelete('cascade');
        $table->string( 'topic'      );
        $table->boolean('multichoice')->default(false);
        $table->boolean('signed'     )->default(false); // Marks if the poll can be voted only by authenticated users
        $table->timestamps();
    });
}

Options:

private $table = 'options';

public function down() {
    Schema::dropIfExists($this->table);
}

public function up() {
    Schema::create($this->table, function(Blueprint $table) {

        $table->increments('id');
        $table->integer(   'poll_id')->unsigned();
        $table->foreign(   'poll_id')->references('id')->on('polls')->onDelete('cascade');
        $table->string(    'name'   );
        $table->integer(   'votes'  )->default(0);
        $table->timestamps();
    });
}

And this is the code that deletes:

    Poll::destroy($id);

I am using sqlite as my DB enging right now.

What am I doing wrong?