Colleen established a trust for the benefit of her son, Liam, for his lifetime. Upon Liam's death, the trust property is to be distributed among Liam's children in such amounts and proportions as Colleen shall direct if she is then living; otherwise, the property will be distributed to Liam's then living issue or, in default thereof, to the American Cancer Society. Identify the reversionary interest retained by Colleen for purposes of 2037. Assume the value of the trust property as of Colleen's death is $10 million. Explain the different results if Colleen's reversionary interest is valued at $400,000 instead of $550,000.