CakePHP有许多关系需要复数类名

I'm working on a cargo shipping application using CakePHP and I've found a workaround to my problem, but I still don't understand what the problem is.

This is my country model

class Country extends AppModel {
    public $recursive = 1;
    public $hasMany = array(
        'Port' => array(
            'className' => 'Ports'
        )
    );
}

This code works. But the following does not.

//Broken example #1
class Country extends AppModel {
    public $recursive = 1;
    public $hasMany = 'Port';
}

And neither does this.

//Broken example #2
class Country extends AppModel {
    public $recursive = 1;
    public $hasMany = 'Ports';
}

my database table is ports. My Model is Port and my controller is PortsController.

The cake documentation would have me believe that I should be using the singular name for the hasMany relationship. And using the singular name works for belongsTo relationships elsewhere in my program.

It's difficult to get debugging info because all the requests are ajax, but From what I'm able to see, the queries aren't any different.

Using the working code, my queries are:

SELECT `Country`.`id`, `Country`.`name` FROM `db`.`countries` AS `Country` WHERE 1 = 1

SELECT `Port`.`id`, `Port`.`country_id`, `Port`.`name` FROM `db`.`ports` AS `Port` WHERE `Port`.`country_id` IN (1, 3, 2)

Using broken example #1, the queries I get are:

SELECT `Country`.`id`, `Country`.`name` FROM `db`.`countries` AS `Country` WHERE 1 = 1

SELECT `Port`.`id`, `Port`.`country_id`, `Port`.`name` FROM `db`.`ports` AS `Port` WHERE `Port`.`country_id` IN (1, 3, 2)

So Why is this model acting so strange?

Edit: Adding Port model

class Port extends AppModel {
    public $belongsTo = array('Country', 'Customer');    
}