Ferdinand Christian Gustav Arnold

Ferdinand Christian Gustav Arnold (24 February 1828 – 8 August 1901)^[1] was a German lichenologist and taxonomist born in Ansbach, Bavaria. Even as a high school student he showed an active interest in botany: "Ich und August Gattinger ... durchstreiften von November 1846 bis zum Spätherbst 1847, Pflanzen sammelnd, die Landschaft von München nach allen Richtungen." ("August Gattinger and I … roamed across the landscape of Munich from November 1846 up to the late autumn 1847, collecting plants, in all directions.").^[2]

He studied jurisprudence in Munich and Heidelberg and during his career practiced law in Eichstätt (1857–77) and Munich (1877–96). He was awarded an honorary doctorate by the University of Munich in 1878. Additionally he was a student of botanists Carl Friedrich Philipp von Martius (1794–1868) and Otto Sendtner (1813–1859), and his spare time was devoted to floristics and classification of plants and fungi.

His initial studies dealt with vascular plants, but his primary focus later shifted to lichens and bryophytes. Well known for his studies of herbarium specimens, his personal herbarium contained approximately 150,000 specimens, largely consisting of lichens and lichenicolous fungi.^[3] He edited and distributed several exsiccatae, among others Lichenes exsiccati [Lichenes Jurae] (1859–1879) and Lichenes Monacenses exsiccati (1889–1900).^[4][5][6] Several fascicles of the series Cladoniae exsiccatae were edited by Heinrich Rehm together with him.^[7] Today this collection is kept at the Botanische Staatssammlung München.

Arnold was the author of Lichenologische Ausflüge in Tirol (Lichenological Excursions in Tyrol), which is still considered to be an important source of information on alpine lichenology. He was a founding member of the Bayerische Botanische Gesellschaft, and in 1878 he received an honorary doctorate from the University of Munich.^[8] Arnold died in Munich in 1901.

Arnold's handwriting is considered exceptionally difficult to read and Hannes Hertel, a director of the Botanische Staatssammlung, devoted significant effort to transcribing Arnold's writing so others could read it.^[9] The journal series Arnoldia, named in his honor, started publication in 1991, devoted to describing the labels, i.e. the "schedae" and annotations of exsiccata series distributed by in the Botanische Staatssammlung.^[10] In 2007, Hertel published the lichen genus Farnoldia, named after Ferdinand Christian Gustav Arnold.^[11]