<p>Stamm von Grau- und Schwarzerle
Gray stem: <a href="//commons.wikimedia.org/wiki/Alnus_incana" title="Alnus incana">Alnus incana</a>
</p>
Black stem: <a href="//commons.wikimedia.org/wiki/Alnus_glutinosa" title="Alnus glutinosa">Alnus glutinosa</a>
No machine-readable author provided. <a href="//commons.wikimedia.org/wiki/User:B.gliwa" title="User:B.gliwa">B.gliwa</a> assumed (based on copyright claims).
CC BY 2.5
No machine-readable source provided. Own work assumed (based on copyright claims).