Pteridologische aantekeningen, 1, Asplenium adiantum-nigrum X A. ruta-muraria in Nederland

In this paper a number of records of the putative hybrid of Asplenium adiantum-nigrum and A. ruta-muraria, found in botanical literature, are discussed. These records bear reference to finds in Spain, France, Italy, Switzerland, and Poland. Some recent authors are in doubt about the existence of this hybrid. In the opinion of the present author a specimen growing on an old wall at Enkhuizen together with a single plant of A. adiantum-nigrum and many of A. ruta-muraria doubtless represents the hybrid in question.