<p>From <i>Köhler's Medizinal-Pflanzen in naturgetreuen Abbildungen mit kurz erläuterndem Texte</i> (Köhler's medicinal plants in natural depictions with short explanatory texts), published by Franz Eugen Köhler in Gera-Untermhaus, Germany, 1887; illustrations by Walther Müller and C.F. Schmid. 
</p><p>From the <a rel="nofollow" class="external text" href="http://caliban.mpiz-koeln.mpg.de/~stueber/koehler/index.html">Köhler Collection</a> at <a rel="nofollow" class="external text" href="http://www.biolib.de">Biolib</a>, the online library of historical biology texts.
<a rel="nofollow" class="external text" href="https://www.flickr.com/search/?s=int&amp;w=76204898@N00&amp;q=%20franzeugenk%C3%B6hler&amp;m=tags">More plant illustrations by F.E. Köhler</a> | <a rel="nofollow" class="external text" href="https://www.flickr.com/search/?w=76204898@N00&amp;q=biolib&amp;m=tags">More Biolib pictures</a>
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<b>[PD]</b> <a rel="nofollow" class="external text" href="http://caliban.mpiz-koeln.mpg.de/~stueber/koehler/COLA.jpg">This picture</a> is in the public domain.
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<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/trialsanderrors/2991880717/">Kola nut (cola acuminata) from Köhler's medicinal plants, 1887</a>