• (a.) Of or pertaining to the Didynamia; containing four stamens disposed in pairs of unequal length.
with two pairs of stamens of unequal length
Of stamens: four in number, two being distinctly longer than the other two. ... (09 Oct 1997) ... 
with two pairs of stamens of unequal length
Having 4 stamens that appear as two pairs of unequal length.
Di·dyn'a·mous adjective (Botany) Of or pertaining to the Didynamia; containing four stamens disposed in pairs of unequal length. 
With four stamens in two pairs of different length.
(of a flower) having four stamens in two pairs of different length.