Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Genus Description - Pet obovate, the 2 upper often differing in size from the 3 lower; outer series of stamens sterile or reduced to scales, the inner series with normal anthers; fr differing from Geranium in that the carpel-beaks separate completely from the stylar column (usually from the top downwards) each such beak typically remaining attached to the basally sharp-pointed carpel-body as a terminal awn, the lower part of which coils hygroscopically; seed smooth, retained within the carpel-body; small herbs with basal or alternate, serrate to more often pinnately divided or dissected lvs and umbel-like cymes of small, pink to purple fls. 75, mostly Mediterranean reg. and Middle East.
stork's bill, filaree