This name is a synonym of Hydrangea macrophylla var. otaksa (E.H. Wilson) L.H. Bailey.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50000607) with original publication details: J. Arnold Arbor. 4(4): 237 1923.
This name was in version 1 of The Plant List, record tro-50000607.