Columbia subject headings:
Harvard subject headings:
Botany--Study and teaching--History--19th century.
Nees van Esenbeck, C. G. (Christian Gottfried), 1776-1856--Congresses.
Princeton subject headings:
Botany--History--19th century--Congresses.
Natural history--History--19th century--Congresses.
Nees von Esenbeck, C. G. (Christian Gottfried), 1776-1858--Congresses.