Information is from Vascular Plant Families, James Payne Smith, Jr., Mad River Press, and Plants of the Chicago Region, Floyd Swink and Gerould Wilhelm, Indiana Academy of Science.
Family Overview - The Rosales
Geraniaceae - the Geranium Family
Diversity and Distribution: Eleven genera and 780 species. Worldwide but especially well represented in the north temperate zone and in South Africa. The cultivated geranium is Pelargonium. The native representatives belong to the genus Geranium, Cranesbill (leaves palmately lobed or trifoliate; usually 10 stamens), with 4 native and 4 introduced species in the Chicago region. We also have the introduced Erodium or Storksbill (with pinnately compound leaves; 5 stamens).
Floral structure:
Significant features: Ours are herbs with palmately or pinnately lobed to compound leaves. Flowers 5-merous. The fruits are elastically dehiscent schizocarps which curl up on a beak. Flowers in cymes or umbels.
Geranium carolinianum mature fruit and leaf. One of the seeds is curved up on the beak (lower left). The other thing is a bug.
Images of Geraniaceae, Texas; source of the fruit and leaf pictures linked above.
Images of Geraniaceae, Hawaii; source of the flower picture above.
The Geraniaceae Group, UK
Geraniaceae Links, UK
Pelargonium Links, UK