This excerpt taken from the AAPL 10-Q filed May 4, 2005.
Delivery; Roll-Over of Fractional Share Interests.
As promptly as practicable after the termination of each offering, the Company shall arrange for the delivery to each participant, as appropriate, of a certificate representing the number of full shares purchased upon exercise of his or her option. No fractional shares shall be issued. Any cash remaining to the credit of a participants account under the Plan after a purchase by him or her of shares at the termination of each offering period which is insufficient to purchase a full share of Common Stock of the Company subject to option shall remain in such participants account and shall be applied to the next succeeding offering period unless the participant has withdrawn as to future offering periods, in which case such cash shall be returned to said participant. Any cash attributable to shares in excess of the number of shares subject to option to the participant (as determined in accordance with Section 7(a) hereof) shall be returned to the participant.