Title: Correspondence
Subjects: Correspondence, Callitriche, Callitrichaceae, Lemna, Wolffia
People: George Engelmann (1809-1884), Elihu Hall (1822-1882), Charles Wright (1811-1885), Karl Andreas Geyer (1809-1853), Alexander Braun (1805-1877), John M. Bigelow (1804-1878), C. F. Austin (1831-1880), Christoph Friedrich Hegelmaier (1833-1906), Nicholas Riehl (1808-1852)