Cambridge Geranium is a hybrid between Geranium macrorrhizum and Geranium dalmaticum. It does not set seed.
Pictured below are:
Cambridge Geranium; 6 inches tall; magenta; an aromatic, carpeting species, and
Geranium x cantabrigiense 'Biokovo'; 6 inches tall; white with a pink blush: this was discovered by Hans Simon of W. Germany as a naturally-occurring clone in the Biokova Mountains of southern Dalmatia.