The varietal epithet alludes to the narrow stems rather than the leaflets which, unlike those of the type variety, are far from filiform.
Source:
Duretto, M.F. (1999). Apiaceae. In: Walsh, N.G.; Entwisle, T.J., Flora of Victoria Vol. 4, Cornaceae to Asteraceae, pp. 256–258. Inkata Press, Melbourne.
