Parmelia borreri (Sm.) Turner in Nederland Kritische kanttekeningen bij de recente vondsten

The author objects to the Dutch Parmelia borreri (Sm.) Turner, found during the last ten years. After a detailed morphological and chemical study of the Dutch collections from both P. borreri and P. subrudecta Nyl. as well as from foreign material (UV, MCT-GE, TLC-EA, chemical reactions) he points out that the recent Dutch P. borreri does not answer to the descriptions given by the various authors such as Clauzade & Roux (1985), Hale (1965), Poelt (1969), Purvis et al. (1992) and. Wirth (1980). The lower surface of P. borreri should be black, which Hale clearly states: ‘The holotype of Parmelia borreri contains atranorine and gyrophoric acid and has a black underside’. The recent Dutch collections however show a variable colour of the lower surface, a feature shared with P. subrudecta. The possession of gyrophoric acid however does not agree.