A Columbia University student who sold marijuana as part of a campus drug-dealing ring is beginning a year of drug treatment that could get his charges dismissed.

Christopher Coles, 20, pleaded guilty yesterday to selling more than a pound of marijuana to an undercover officer and steering the officer to another student to buy the stimulant Adderall.

Coles will be allowed to withdraw the plea, and the case will be dismissed, if he succeeds in inpatient rehabilitation.

Three other students who allegedly participated in the ring have pleaded guilty to various charges.