German pharmacist who owned a succesful pharmacy (1841-1878) in Hamburg. He was an enthusiastic botanist, latterly an algologist, and amassed an extensive private herbarium mostly consisting of material from other collectors. Only material from Europe was collected by Sonder, though some Scandinavian material was from C.A. Agardh. Most of his important South African holdings were collected by C.F. Ecklon, W.H. Harvey, C.P. Thunberg and C.L.P.Zeyher. His Australian specimens, mainly collected by J.A.L. Preiss and F.J.H. von Mueller were loaned to G. Bentham for compilation of his Flora Australiensis. American material sometimes attributed to Sonder was mainly collected by J.G.C. Lehmann. Sonder published on his own local flora and that of South Africa, specialising in Ericaceae and algae. He eventually sold his herbarium, some 9,000 specimens purchased by S (1875) and the remaining 250,000 specimens being purchased by MEL (1883). A large part of the algal holdings at HBG originate from Sonder and some algal specimens at BM are also from Sonder's herbarium. Many plants are named in his honour including the algal genera Sonderella F. Schmitz, Sonderia F. Muell., Sonderopelta Womersley & Sinkora and Sonderophycus Denizot.