Source: Compuware APM

As a companion piece to the comScore report Monday that Americans have spent a record $18.7 billion online so far this holiday season — up 15% from last year — consider this chart from Compuware APM showing the relative contributions of the two leading platforms for what it calls “couch commerce”: Apple’s AAPL iPad and iPhone.

Together, according to an earlier IBM study, the two devices accounted for 10.2% of Black Friday’s online retail traffic.