Dans sa Division II, chapitre VIII, section 1, article 60.7, le Code de Shenzhen (ICN) stipule que :

«Diacritical signs are not used in scientific names. When names (either new or old) are drawn from words in which such signs appear, the signs are to be suppressed with the necessary transcription of the letters so modified; for example ä, ö, ü become, respectively, ae, oe, ue
(not æ or œ, see below);
é, è, ê become e; ñ becomes n; ø becomes oe (not œ);
å becomes ao.
The diaeresis, indicating that a vowel is to be pronounced separately from the preceding vowel (as in Cephaëlis, Isoëtes), is a phonetic device that is not considered to alter the spelling; as such, its use is optional.
The ligatures æ and œ,
indicating that the letters are pronounced together, are to be replaced by the separate letters ae and oe.»

C'est la raison pour laquelle se trouvent toujours dans de vieilles flores encore parfois intéressantes des noms comme par ex. : Æsculus hippocastanum, Æthusa cynapium ou Allium sphærocephalum, Centaurium erythræa, Anagallis fœmina, Fœniculum vulgare, etc...