That depends on which type of driver you are referring to, constant current, or constant voltage.
To wire in series, with a single constant current model, the total Voltage of the cobs together, needs to be lower than the total voltage available from the driver.
What is the voltage requirement of the COB?
If you were to use a constant voltage driver, you will wire in parallel, then you can run as many cobs as you wish, provided the CV driver is matching the voltage requirement of the COB.